Experiment: zero-copy TCP send

2023-11-04 01:34:18 +03:00
63 changed files with 355 additions and 3796 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,6 @@ cmake_minimum_required(VERSION 2.8.12)

 project(vitastor)

-set(VERSION "1.2.0")
+set(VERSION "1.1.0")

 add_subdirectory(src)
--- a/csi/Makefile
+++ b/csi/Makefile
@@ -1,4 +1,4 @@
-VERSION ?= v1.2.0
+VERSION ?= v1.1.0

 all: build push

--- a/csi/deploy/004-csi-nodeplugin.yaml
+++ b/csi/deploy/004-csi-nodeplugin.yaml
@@ -49,7 +49,7 @@ spec:
            capabilities:
              add: ["SYS_ADMIN"]
            allowPrivilegeEscalation: true
-          image: vitalif/vitastor-csi:v1.2.0
+          image: vitalif/vitastor-csi:v1.1.0
          args:
            - "--node=$(NODE_ID)"
            - "--endpoint=$(CSI_ENDPOINT)"
--- a/csi/deploy/007-csi-provisioner.yaml
+++ b/csi/deploy/007-csi-provisioner.yaml
@@ -121,7 +121,7 @@ spec:
            privileged: true
            capabilities:
              add: ["SYS_ADMIN"]
-          image: vitalif/vitastor-csi:v1.2.0
+          image: vitalif/vitastor-csi:v1.1.0
          args:
            - "--node=$(NODE_ID)"
            - "--endpoint=$(CSI_ENDPOINT)"
--- a/csi/src/config.go
+++ b/csi/src/config.go
@@ -5,7 +5,7 @@ package vitastor

 const (
    vitastorCSIDriverName    = "csi.vitastor.io"
-    vitastorCSIDriverVersion = "1.2.0"
+    vitastorCSIDriverVersion = "1.1.0"
 )

 // Config struct fills the parameters of request or user input
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,10 +1,10 @@
-vitastor (1.2.0-1) unstable; urgency=medium
+vitastor (1.1.0-1) unstable; urgency=medium

  * Bugfixes

 -- Vitaliy Filippov <vitalif@yourcmc.ru>  Fri, 03 Jun 2022 02:09:44 +0300

-vitastor (1.2.0-1) unstable; urgency=medium
+vitastor (1.1.0-1) unstable; urgency=medium

  * Implement NFS proxy
  * Add documentation
--- a/debian/vitastor.Dockerfile
+++ b/debian/vitastor.Dockerfile
@@ -35,8 +35,8 @@ RUN set -e -x; \
    mkdir -p /root/packages/vitastor-$REL; \
    rm -rf /root/packages/vitastor-$REL/*; \
    cd /root/packages/vitastor-$REL; \
-    cp -r /root/vitastor vitastor-1.2.0; \
-    cd vitastor-1.2.0; \
+    cp -r /root/vitastor vitastor-1.1.0; \
+    cd vitastor-1.1.0; \
    ln -s /root/fio-build/fio-*/ ./fio; \
    FIO=$(head -n1 fio/debian/changelog | perl -pe 's/^.*\((.*?)\).*$/$1/'); \
    ls /usr/include/linux/raw.h || cp ./debian/raw.h /usr/include/linux/raw.h; \
@@ -49,8 +49,8 @@ RUN set -e -x; \
    rm -rf a b; \
    echo "dep:fio=$FIO" > debian/fio_version; \
    cd /root/packages/vitastor-$REL; \
-    tar --sort=name --mtime='2020-01-01' --owner=0 --group=0 --exclude=debian -cJf vitastor_1.2.0.orig.tar.xz vitastor-1.2.0; \
-    cd vitastor-1.2.0; \
+    tar --sort=name --mtime='2020-01-01' --owner=0 --group=0 --exclude=debian -cJf vitastor_1.1.0.orig.tar.xz vitastor-1.1.0; \
+    cd vitastor-1.1.0; \
    V=$(head -n1 debian/changelog | perl -pe 's/^.*\((.*?)\).*$/$1/'); \
    DEBFULLNAME="Vitaliy Filippov <vitalif@yourcmc.ru>" dch -D $REL -v "$V""$REL" "Rebuild for $REL"; \
    DEB_BUILD_OPTIONS=nocheck dpkg-buildpackage --jobs=auto -sa; \
--- a/docs/config/network.en.md
+++ b/docs/config/network.en.md
@@ -20,7 +20,6 @@ between clients, OSDs and etcd.
 - [rdma_max_msg](#rdma_max_msg)
 - [rdma_max_recv](#rdma_max_recv)
 - [rdma_max_send](#rdma_max_send)
- [rdma_odp](#rdma_odp)
 - [peer_connect_interval](#peer_connect_interval)
 - [peer_connect_timeout](#peer_connect_timeout)
 - [osd_idle_timeout](#osd_idle_timeout)
@@ -69,14 +68,11 @@ but they are not connected to the cluster.
 - Type: string

 RDMA device name to use for Vitastor OSD communications (for example,
-"rocep5s0f0"). Now Vitastor supports all adapters, even ones without
-ODP support, like Mellanox ConnectX-3 and non-Mellanox cards.
-
-Versions up to Vitastor 1.2.0 required ODP which is only present in
-Mellanox ConnectX >= 4. See also [rdma_odp](#rdma_odp).
-
-Run `ibv_devinfo -v` as root to list available RDMA devices and their
-features.
+"rocep5s0f0"). Please note that Vitastor RDMA requires Implicit On-Demand
+Paging (Implicit ODP) and Scatter/Gather (SG) support from the RDMA device
+to work. For example, Mellanox ConnectX-3 and older adapters don't have
+Implicit ODP, so they're unsupported by Vitastor. Run `ibv_devinfo -v` as
+root to list available RDMA devices and their features.

 Remember that you also have to configure your network switches if you use
 RoCE/RoCEv2, otherwise you may experience unstable performance. Refer to
@@ -151,28 +147,6 @@ less than `rdma_max_recv` so the receiving side doesn't run out of buffers.
 Doesn't affect memory usage - additional memory isn't allocated for send
 operations.

-## rdma_odp
-
- Type: boolean
- Default: false
-
-Use RDMA with On-Demand Paging. ODP is currently only available on Mellanox
-ConnectX-4 and newer adapters. ODP allows to not register memory explicitly
-for RDMA adapter to be able to use it. This, in turn, allows to skip memory
-copying during sending. One would think this should improve performance, but
-**in reality** RDMA performance with ODP is **drastically** worse. Example
-3-node cluster with 8 NVMe in each node and 2*25 GBit/s ConnectX-6 RDMA network
-without ODP pushes 3950000 read iops, but only 239000 iops with ODP...
-
-This happens because Mellanox ODP implementation seems to be based on
-message retransmissions when the adapter doesn't know about the buffer yet -
-it likely uses standard "RNR retransmissions" (RNR = receiver not ready)
-which is generally slow in RDMA/RoCE networks. Here's a presentation about
-it from ISPASS-2021 conference: https://tkygtr6.github.io/pub/ISPASS21_slides.pdf
-
-ODP support is retained in the code just in case a good ODP implementation
-appears one day.
-
 ## peer_connect_interval

 - Type: seconds
--- a/docs/config/network.ru.md
+++ b/docs/config/network.ru.md
@@ -20,7 +20,6 @@
 - [rdma_max_msg](#rdma_max_msg)
 - [rdma_max_recv](#rdma_max_recv)
 - [rdma_max_send](#rdma_max_send)
- [rdma_odp](#rdma_odp)
 - [peer_connect_interval](#peer_connect_interval)
 - [peer_connect_timeout](#peer_connect_timeout)
 - [osd_idle_timeout](#osd_idle_timeout)
@@ -72,15 +71,12 @@ RDMA может быть нужно только если у клиентов е
 - Тип: строка

 Название RDMA-устройства для связи с Vitastor OSD (например, "rocep5s0f0").
-Сейчас Vitastor поддерживает все модели адаптеров, включая те, у которых
-нет поддержки ODP, то есть вы можете использовать RDMA с ConnectX-3 и
-картами производства не Mellanox.
-
-Версии Vitastor до 1.2.0 включительно требовали ODP, который есть только
-на Mellanox ConnectX 4 и более новых. См. также [rdma_odp](#rdma_odp).
-
-Запустите `ibv_devinfo -v` от имени суперпользователя, чтобы посмотреть
-список доступных RDMA-устройств, их параметры и возможности.
+Имейте в виду, что поддержка RDMA в Vitastor требует функций устройства
+Implicit On-Demand Paging (Implicit ODP) и Scatter/Gather (SG). Например,
+адаптеры Mellanox ConnectX-3 и более старые не поддерживают Implicit ODP и
+потому не поддерживаются в Vitastor. Запустите `ibv_devinfo -v` от имени
+суперпользователя, чтобы посмотреть список доступных RDMA-устройств, их
+параметры и возможности.

 Обратите внимание, что если вы используете RoCE/RoCEv2, вам также необходимо
 правильно настроить для него коммутаторы, иначе вы можете столкнуться с
@@ -159,29 +155,6 @@ OSD в любом случае согласовывают реальное зн
 Не влияет на потребление памяти - дополнительная память на операции отправки
 не выделяется.

-## rdma_odp
-
- Тип: булево (да/нет)
- Значение по умолчанию: false
-
-Использовать RDMA с On-Demand Paging. ODP - функция, доступная пока что
-исключительно на адаптерах Mellanox ConnectX-4 и более новых. ODP позволяет
-не регистрировать память для её использования RDMA-картой. Благодаря этому
-можно не копировать данные при отправке их в сеть и, казалось бы, это должно
-улучшать производительность - но **по факту** получается так, что
-производительность только ухудшается, причём сильно. Пример - на 3-узловом
-кластере с 8 NVMe в каждом узле и сетью 2*25 Гбит/с на чтение с RDMA без ODP
-удаётся снять 3950000 iops, а с ODP - всего 239000 iops...
-
-Это происходит из-за того, что реализация ODP у Mellanox неоптимальная и
-основана на повторной передаче сообщений, когда карте не известен буфер -
-вероятно, на стандартных "RNR retransmission" (RNR = receiver not ready).
-А данные повторные передачи в RDMA/RoCE - всегда очень медленная штука.
-Презентация на эту тему с конференции ISPASS-2021: https://tkygtr6.github.io/pub/ISPASS21_slides.pdf
-
-Возможность использования ODP сохранена в коде на случай, если вдруг в один
-прекрасный день появится хорошая реализация ODP.
-
 ## peer_connect_interval

 - Тип: секунды
--- a/docs/config/src/network.yml
+++ b/docs/config/src/network.yml
@@ -30,6 +30,18 @@
    будут использоваться обычные синхронные системные вызовы send/recv. Для OSD
    это бессмысленно, так как OSD в любом случае нуждается в io_uring, но, в
    принципе, это может применяться для клиентов со старыми версиями ядра.
+- name: use_zerocopy_send
+  type: bool
+  default: false
+  info: |
+    If true, OSDs and clients will attempt to use TCP zero-copy send
+    (MSG_ZEROCOPY) for big buffers. It's recommended to raise net.ipv4.tcp_wmem
+    and net.core.wmem_max sysctls when using this mode.
+  info_ru: |
+    Если установлено в true, то OSD и клиенты будут стараться использовать
+    TCP-отправку без копирования (MSG_ZEROCOPY) для больших буферов данных.
+    Рекомендуется поднять значения sysctl net.ipv4.tcp_wmem и net.core.wmem_max
+    при использовании этого режима.
 - name: use_rdma
  type: bool
  default: true
@@ -48,14 +60,11 @@
  type: string
  info: |
    RDMA device name to use for Vitastor OSD communications (for example,
-    "rocep5s0f0"). Now Vitastor supports all adapters, even ones without
-    ODP support, like Mellanox ConnectX-3 and non-Mellanox cards.
-
-    Versions up to Vitastor 1.2.0 required ODP which is only present in
-    Mellanox ConnectX >= 4. See also [rdma_odp](#rdma_odp).
-
-    Run `ibv_devinfo -v` as root to list available RDMA devices and their
-    features.
+    "rocep5s0f0"). Please note that Vitastor RDMA requires Implicit On-Demand
+    Paging (Implicit ODP) and Scatter/Gather (SG) support from the RDMA device
+    to work. For example, Mellanox ConnectX-3 and older adapters don't have
+    Implicit ODP, so they're unsupported by Vitastor. Run `ibv_devinfo -v` as
+    root to list available RDMA devices and their features.

    Remember that you also have to configure your network switches if you use
    RoCE/RoCEv2, otherwise you may experience unstable performance. Refer to
@@ -64,15 +73,12 @@
    PFC (Priority Flow Control) and ECN (Explicit Congestion Notification).
  info_ru: |
    Название RDMA-устройства для связи с Vitastor OSD (например, "rocep5s0f0").
-    Сейчас Vitastor поддерживает все модели адаптеров, включая те, у которых
-    нет поддержки ODP, то есть вы можете использовать RDMA с ConnectX-3 и
-    картами производства не Mellanox.
-
-    Версии Vitastor до 1.2.0 включительно требовали ODP, который есть только
-    на Mellanox ConnectX 4 и более новых. См. также [rdma_odp](#rdma_odp).
-
-    Запустите `ibv_devinfo -v` от имени суперпользователя, чтобы посмотреть
-    список доступных RDMA-устройств, их параметры и возможности.
+    Имейте в виду, что поддержка RDMA в Vitastor требует функций устройства
+    Implicit On-Demand Paging (Implicit ODP) и Scatter/Gather (SG). Например,
+    адаптеры Mellanox ConnectX-3 и более старые не поддерживают Implicit ODP и
+    потому не поддерживаются в Vitastor. Запустите `ibv_devinfo -v` от имени
+    суперпользователя, чтобы посмотреть список доступных RDMA-устройств, их
+    параметры и возможности.

    Обратите внимание, что если вы используете RoCE/RoCEv2, вам также необходимо
    правильно настроить для него коммутаторы, иначе вы можете столкнуться с
@@ -166,45 +172,6 @@
    у принимающей стороны в процессе работы не заканчивались буферы на приём.
    Не влияет на потребление памяти - дополнительная память на операции отправки
    не выделяется.
- name: rdma_odp
-  type: bool
-  default: false
-  online: false
-  info: |
-    Use RDMA with On-Demand Paging. ODP is currently only available on Mellanox
-    ConnectX-4 and newer adapters. ODP allows to not register memory explicitly
-    for RDMA adapter to be able to use it. This, in turn, allows to skip memory
-    copying during sending. One would think this should improve performance, but
-    **in reality** RDMA performance with ODP is **drastically** worse. Example
-    3-node cluster with 8 NVMe in each node and 2*25 GBit/s ConnectX-6 RDMA network
-    without ODP pushes 3950000 read iops, but only 239000 iops with ODP...
-
-    This happens because Mellanox ODP implementation seems to be based on
-    message retransmissions when the adapter doesn't know about the buffer yet -
-    it likely uses standard "RNR retransmissions" (RNR = receiver not ready)
-    which is generally slow in RDMA/RoCE networks. Here's a presentation about
-    it from ISPASS-2021 conference: https://tkygtr6.github.io/pub/ISPASS21_slides.pdf
-
-    ODP support is retained in the code just in case a good ODP implementation
-    appears one day.
-  info_ru: |
-    Использовать RDMA с On-Demand Paging. ODP - функция, доступная пока что
-    исключительно на адаптерах Mellanox ConnectX-4 и более новых. ODP позволяет
-    не регистрировать память для её использования RDMA-картой. Благодаря этому
-    можно не копировать данные при отправке их в сеть и, казалось бы, это должно
-    улучшать производительность - но **по факту** получается так, что
-    производительность только ухудшается, причём сильно. Пример - на 3-узловом
-    кластере с 8 NVMe в каждом узле и сетью 2*25 Гбит/с на чтение с RDMA без ODP
-    удаётся снять 3950000 iops, а с ODP - всего 239000 iops...
-
-    Это происходит из-за того, что реализация ODP у Mellanox неоптимальная и
-    основана на повторной передаче сообщений, когда карте не известен буфер -
-    вероятно, на стандартных "RNR retransmission" (RNR = receiver not ready).
-    А данные повторные передачи в RDMA/RoCE - всегда очень медленная штука.
-    Презентация на эту тему с конференции ISPASS-2021: https://tkygtr6.github.io/pub/ISPASS21_slides.pdf
-
-    Возможность использования ODP сохранена в коде на случай, если вдруг в один
-    прекрасный день появится хорошая реализация ODP.
 - name: peer_connect_interval
  type: sec
  min: 1
--- a/docs/installation/kubernetes.en.md
+++ b/docs/installation/kubernetes.en.md
@@ -17,15 +17,4 @@ and apply all `NNN-*.yaml` manifests to your Kubernetes installation:
 for i in ./???-*.yaml; do kubectl apply -f $i; done
 ```

-After that you'll be able to create PersistentVolumes.
-
-## Features
-
-Vitastor CSI supports:
- Kubernetes starting with 1.20 (or 1.17 for older vitastor-csi <= 1.1.0)
- Filesystem RWO (ReadWriteOnce) volumes. Example: [PVC](../../csi/deploy/example-pvc.yaml), [pod](../../csi/deploy/example-test-pod.yaml)
- Raw block RWX (ReadWriteMany) volumes. Example: [PVC](../../csi/deploy/example-pvc-block.yaml), [pod](../../csi/deploy/example-test-pod-block.yaml)
- Volume expansion
- Volume snapshots. Example: [snapshot class](../../csi/deploy/example-snapshot-class.yaml), [snapshot](../../csi/deploy/example-snapshot.yaml), [clone](../../csi/deploy/example-snapshot-clone.yaml)
-
-Remember that to use snapshots with CSI you also have to install [Snapshot Controller and CRDs](https://kubernetes-csi.github.io/docs/snapshot-controller.html#deployment).
+After that you'll be able to create PersistentVolumes. See example in [csi/deploy/example-pvc.yaml](../../csi/deploy/example-pvc.yaml).
--- a/docs/installation/kubernetes.ru.md
+++ b/docs/installation/kubernetes.ru.md
@@ -17,15 +17,4 @@
 for i in ./???-*.yaml; do kubectl apply -f $i; done
 ```

-После этого вы сможете создавать PersistentVolume.
-
-## Возможности
-
-CSI-плагин Vitastor поддерживает:
- Версии Kubernetes, начиная с 1.20 (или с 1.17 для более старых vitastor-csi <= 1.1.0)
- Файловые RWO (ReadWriteOnce) тома. Пример: [PVC](../../csi/deploy/example-pvc.yaml), [под](../../csi/deploy/example-test-pod.yaml)
- Сырые блочные RWX (ReadWriteMany) тома. Пример: [PVC](../../csi/deploy/example-pvc-block.yaml), [под](../../csi/deploy/example-test-pod-block.yaml)
- Расширение размера томов
- Снимки томов. Пример: [класс снимков](../../csi/deploy/example-snapshot-class.yaml), [снимок](../../csi/deploy/example-snapshot.yaml), [клон снимка](../../csi/deploy/example-snapshot-clone.yaml)
-
-Не забывайте, что для использования снимков нужно сначала установить [контроллер снимков и CRD](https://kubernetes-csi.github.io/docs/snapshot-controller.html#deployment).
+После этого вы сможете создавать PersistentVolume. Пример смотрите в файле [csi/deploy/example-pvc.yaml](../../csi/deploy/example-pvc.yaml).
--- a/docs/usage/qemu.en.md
+++ b/docs/usage/qemu.en.md
@@ -127,46 +127,19 @@ Linux kernel, starting with version 5.15, supports a new interface for attaching
 to the host - VDUSE (vDPA Device in Userspace). QEMU, starting with 7.2, has support for
 exporting QEMU block devices over this protocol using qemu-storage-daemon.

-VDUSE is currently the best interface to attach Vitastor disks as kernel devices because:
- It avoids data copies and thus achieves much better performance than [NBD](nbd.en.md)
- It doesn't have NBD timeout problem - the device doesn't die if an operation executes for too long
- It doesn't have hung device problem - if the userspace process dies it can be restarted (!)
-  and block device will continue operation
- It doesn't seem to have the device number limit
+VDUSE has the same problem as other FUSE-like interfaces in Linux: if a userspace process hangs,
+for example, if it loses connectivity with Vitastor cluster - active processes doing I/O may
+hang in the D state (uninterruptible sleep) and you won't be able to kill them even with kill -9.
+In this case reboot will be the only way to remove VDUSE devices from system.

-Example performance comparison:
-
-|                      | direct fio  | NBD         | VDUSE       |
-|----------------------|-------------|-------------|-------------|
-| linear write         | 3.85 GB/s   | 1.12 GB/s   | 3.85 GB/s   |
-| 4k random write Q128 | 240000 iops | 120000 iops | 178000 iops |
-| 4k random write Q1   | 9500 iops   | 7620 iops   | 7640 iops   |
-| linear read          | 4.3 GB/s    | 1.8 GB/s    | 2.85 GB/s   |
-| 4k random read Q128  | 287000 iops | 140000 iops | 189000 iops |
-| 4k random read Q1    | 9600 iops   | 7640 iops   | 7780 iops   |
+On the other hand, VDUSE is faster than [NBD](nbd.en.md), so you may prefer to use it if
+performance is important for you. Approximate performance numbers:
+direct fio benchmark - 115000 iops, NBD - 60000 iops, VDUSE - 90000 iops.

 To try VDUSE you need at least Linux 5.15, built with VDUSE support
-(CONFIG_VIRTIO_VDPA=m, CONFIG_VDPA_USER=m, CONFIG_VIRTIO_VDPA=m).
-
-Debian Linux kernels have these options disabled by now, so if you want to try it on Debian,
-use a kernel from Ubuntu [kernel-ppa/mainline](https://kernel.ubuntu.com/~kernel-ppa/mainline/), Proxmox,
-or build modules for Debian kernel manually:
-
-```
-mkdir build
-cd build
-apt-get install linux-headers-`uname -r`
-apt-get build-dep linux-image-`uname -r`-unsigned
-apt-get source linux-image-`uname -r`-unsigned
-cd linux*/drivers/vdpa
-make -C /lib/modules/`uname -r`/build M=$PWD CONFIG_VDPA=m CONFIG_VDPA_USER=m CONFIG_VIRTIO_VDPA=m -j8 modules modules_install
-cat Module.symvers >> /lib/modules/`uname -r`/build/Module.symvers
-cd ../virtio
-make -C /lib/modules/`uname -r`/build M=$PWD CONFIG_VDPA=m CONFIG_VDPA_USER=m CONFIG_VIRTIO_VDPA=m -j8 modules modules_install
-depmod -a
-```
-
-You also need `vdpa` tool from the `iproute2` package.
+(CONFIG_VIRTIO_VDPA=m and CONFIG_VDPA_USER=m). Debian Linux kernels have these options
+disabled by now, so if you want to try it on Debian, use a kernel from Ubuntu
+[kernel-ppa/mainline](https://kernel.ubuntu.com/~kernel-ppa/mainline/) or Proxmox.

 Commands to attach Vitastor image as a VDUSE device:

@@ -179,7 +152,7 @@ qemu-storage-daemon --daemonize --blockdev '{"node-name":"test1","driver":"vitas
 vdpa dev add name test1 mgmtdev vduse
 ```

-After running these commands, `/dev/vda` device will appear in the system and you'll be able to
+After running these commands /dev/vda device will appear in the system and you'll be able to
 use it as a normal disk.

 To remove the device:
--- a/docs/usage/qemu.ru.md
+++ b/docs/usage/qemu.ru.md
@@ -129,47 +129,19 @@ qemu-system-x86_64 -enable-kvm -m 2048 -M accel=kvm,memory-backend=mem \
 к системе - VDUSE (vDPA Device in Userspace), а в QEMU, начиная с версии 7.2, есть поддержка
 экспорта блочных устройств QEMU по этому протоколу через qemu-storage-daemon.

-VDUSE - на данный момент лучший интерфейс для подключения дисков Vitastor в виде блочных
-устройств на уровне ядра, ибо:
- VDUSE не копирует данные и поэтому достигает значительно лучшей производительности, чем [NBD](nbd.ru.md)
- Также оно не имеет проблемы NBD-таймаута - устройство не умирает, если операция выполняется слишком долго
- Также оно не имеет проблемы подвисающих устройств - если процесс-обработчик умирает, его можно
-  перезапустить (!) и блочное устройство продолжит работать
- По-видимому, у него нет предела числа подключаемых в систему устройств
+VDUSE страдает общей проблемой FUSE-подобных интерфейсов в Linux: если пользовательский процесс
+подвиснет, например, если будет потеряна связь с кластером Vitastor - читающие/пишущие в кластер
+процессы могут "залипнуть" в состоянии D (непрерываемый сон) и их будет невозможно убить даже
+через kill -9. В этом случае удалить из системы устройство можно только перезагрузившись.

-Пример сравнения производительности:
+С другой стороны, VDUSE быстрее по сравнению с [NBD](nbd.ru.md), поэтому его может
+быть предпочтительно использовать там, где производительность важнее. Порядок показателей:
+прямое тестирование через fio - 115000 iops, NBD - 60000 iops, VDUSE - 90000 iops.

-|                          | Прямой fio  | NBD         | VDUSE       |
-|--------------------------|-------------|-------------|-------------|
-| линейная запись          | 3.85 GB/s   | 1.12 GB/s   | 3.85 GB/s   |
-| 4k случайная запись Q128 | 240000 iops | 120000 iops | 178000 iops |
-| 4k случайная запись Q1   | 9500 iops   | 7620 iops   | 7640 iops   |
-| линейное чтение          | 4.3 GB/s    | 1.8 GB/s    | 2.85 GB/s   |
-| 4k случайное чтение Q128 | 287000 iops | 140000 iops | 189000 iops |
-| 4k случайное чтение Q1   | 9600 iops   | 7640 iops   | 7780 iops   |
-
-Чтобы попробовать VDUSE, вам нужно ядро Linux как минимум версии 5.15, собранное с поддержкой
-VDUSE (CONFIG_VIRTIO_VDPA=m, CONFIG_VDPA_USER=m, CONFIG_VIRTIO_VDPA=m).
-
-В ядрах в Debian Linux поддержка пока отключена по умолчанию, так что чтобы попробовать VDUSE
-на Debian, поставьте ядро из Ubuntu [kernel-ppa/mainline](https://kernel.ubuntu.com/~kernel-ppa/mainline/),
-из Proxmox или соберите модули для ядра Debian вручную:
-
-```
-mkdir build
-cd build
-apt-get install linux-headers-`uname -r`
-apt-get build-dep linux-image-`uname -r`-unsigned
-apt-get source linux-image-`uname -r`-unsigned
-cd linux*/drivers/vdpa
-make -C /lib/modules/`uname -r`/build M=$PWD CONFIG_VDPA=m CONFIG_VDPA_USER=m CONFIG_VIRTIO_VDPA=m -j8 modules modules_install
-cat Module.symvers >> /lib/modules/`uname -r`/build/Module.symvers
-cd ../virtio
-make -C /lib/modules/`uname -r`/build M=$PWD CONFIG_VDPA=m CONFIG_VDPA_USER=m CONFIG_VIRTIO_VDPA=m -j8 modules modules_install
-depmod -a
-```
-
-Также вам понадобится консольная утилита `vdpa` из пакета `iproute2`.
+Чтобы использовать VDUSE, вам нужно ядро Linux версии хотя бы 5.15, собранное с поддержкой
+VDUSE (CONFIG_VIRTIO_VDPA=m и CONFIG_VDPA_USER=m). В ядрах в Debian Linux поддержка пока
+отключена - если хотите попробовать эту функцию на Debian, поставьте ядро из Ubuntu
+[kernel-ppa/mainline](https://kernel.ubuntu.com/~kernel-ppa/mainline/) или из Proxmox.

 Команды для подключения виртуального диска через VDUSE:

@@ -182,7 +154,7 @@ qemu-storage-daemon --daemonize --blockdev '{"node-name":"test1","driver":"vitas
 vdpa dev add name test1 mgmtdev vduse
 ```

-После этого в системе появится устройство `/dev/vda`, которое можно будет использовать как
+После этого в системе появится устройство /dev/vda, которое можно будет использовать как
 обычный диск.

 Для удаления устройства из системы:
--- a/2
+++ b/2
--- a/mon/mon.js
+++ b/mon/mon.js
@@ -65,6 +65,7 @@ const etcd_tree = {
            // client and osd
            tcp_header_buffer_size: 65536,
            use_sync_send_recv: false,
+            use_zerocopy_send: false,
            use_rdma: true,
            rdma_device: null, // for example, "rocep5s0f0"
            rdma_port_num: 1,
@@ -403,7 +404,6 @@ class Mon
        this.ws_alive = false;
        this.ws_keepalive_timer = null;
        this.on_stop_cb = () => this.on_stop(0).catch(console.error);
-        this.recheck_pgs_active = false;
    }

    parse_etcd_addresses(addrs)
@@ -693,27 +693,8 @@ class Mon
        });
    }

-    // Schedule save_last_clean() to to run after a small timeout (1s) (to not spam etcd)
-    schedule_save_last_clean()
-    {
-        if (!this.save_last_clean_timer)
-        {
-            this.save_last_clean_timer = setTimeout(() =>
-            {
-                this.save_last_clean_timer = null;
-                this.save_last_clean().catch(this.die);
-            }, this.config.mon_change_timeout || 1000);
-        }
-    }
-
    async save_last_clean()
    {
-        if (this.save_last_clean_running)
-        {
-            this.schedule_save_last_clean();
-            return;
-        }
-        this.save_last_clean_running = true;
        // last_clean_pgs is used to avoid extra data move when observing a series of changes in the cluster
        const new_clean_pgs = { items: {} };
    next_pool:
@@ -750,7 +731,6 @@ class Mon
                value: b64(JSON.stringify(this.state.history.last_clean_pgs))
            } } ],
        }, this.etcd_start_timeout, 0);
-        this.save_last_clean_running = false;
    }

    get_mon_state()
@@ -1224,12 +1204,6 @@ class Mon

    async recheck_pgs()
    {
-        if (this.recheck_pgs_active)
-        {
-            this.schedule_recheck();
-            return;
-        }
-        this.recheck_pgs_active = true;
        // Take configuration and state, check it against the stored configuration hash
        // Recalculate PGs and save them to etcd if the configuration is changed
        // FIXME: Do not change anything if the distribution is good and random enough and no PGs are degraded
@@ -1251,7 +1225,6 @@ class Mon
                    // Pool deleted. Delete all PGs, but first stop them.
                    if (!await this.stop_all_pgs(pool_id))
                    {
-                        this.recheck_pgs_active = false;
                        this.schedule_recheck();
                        return;
                    }
@@ -1320,16 +1293,9 @@ class Mon
                        // PG count changed. Need to bring all PGs down.
                        if (!await this.stop_all_pgs(pool_id))
                        {
-                            this.recheck_pgs_active = false;
                            this.schedule_recheck();
                            return;
                        }
-                    }
-                    if (prev_pgs.length != pool_cfg.pg_count)
-                    {
-                        // Scale PG count
-                        // Do it even if old_pg_count is already equal to pool_cfg.pg_count,
-                        // because last_clean_pgs may still contain the old number of PGs
                        const new_pg_history = [];
                        PGUtil.scale_pg_count(prev_pgs, real_prev_pgs, pg_history, new_pg_history, pool_cfg.pg_count);
                        pg_history = new_pg_history;
@@ -1431,7 +1397,6 @@ class Mon
                await this.save_pg_config(new_config_pgs);
            }
        }
-        this.recheck_pgs_active = false;
    }

    async save_pg_config(new_config_pgs, etcd_request = { compare: [], success: [] })
@@ -1481,6 +1446,7 @@ class Mon
    }

    // Schedule a recheck to run after a small timeout (1s)
+    // If already scheduled, cancel previous timer and schedule it again
    // This is required for multiple change events to trigger at most 1 recheck in 1s
    schedule_recheck()
    {
@@ -1498,7 +1464,7 @@ class Mon
    {
        const zero_stats = { op: { bps: 0n, iops: 0n, lat: 0n }, subop: { iops: 0n, lat: 0n }, recovery: { bps: 0n, iops: 0n } };
        const diff = { op_stats: {}, subop_stats: {}, recovery_stats: {}, inode_stats: {} };
-        if (!st || !st.time || !prev || !prev.time || prev.time >= st.time)
+        if (!st || !st.time || !prev || prev.time >= st.time)
        {
            return prev_diff || diff;
        }
--- a/mon/package.json
+++ b/mon/package.json
@@ -1,6 +1,6 @@
 {
  "name": "vitastor-mon",
-  "version": "1.2.0",
+  "version": "1.1.0",
  "description": "Vitastor SDS monitor service",
  "main": "mon-main.js",
  "scripts": {
--- a/patches/cinder-vitastor.py
+++ b/patches/cinder-vitastor.py
@@ -50,7 +50,7 @@ from cinder.volume import configuration
 from cinder.volume import driver
 from cinder.volume import volume_utils

-VERSION = '1.2.0'
+VERSION = '1.1.0'

 LOG = logging.getLogger(__name__)

--- a/rpm/build-tarball.sh
+++ b/rpm/build-tarball.sh
@@ -24,4 +24,4 @@ rm fio
 mv fio-copy fio
 FIO=`rpm -qi fio | perl -e 'while(<>) { /^Epoch[\s:]+(\S+)/ && print "$1:"; /^Version[\s:]+(\S+)/ && print $1; /^Release[\s:]+(\S+)/ && print "-$1"; }'`
 perl -i -pe 's/(Requires:\s*fio)([^\n]+)?/$1 = '$FIO'/' $VITASTOR/rpm/vitastor-el$EL.spec
-tar --transform 's#^#vitastor-1.2.0/#' --exclude 'rpm/*.rpm' -czf $VITASTOR/../vitastor-1.2.0$(rpm --eval '%dist').tar.gz *
+tar --transform 's#^#vitastor-1.1.0/#' --exclude 'rpm/*.rpm' -czf $VITASTOR/../vitastor-1.1.0$(rpm --eval '%dist').tar.gz *
--- a/rpm/vitastor-el7.Dockerfile
+++ b/rpm/vitastor-el7.Dockerfile
@@ -35,7 +35,7 @@ ADD . /root/vitastor
 RUN set -e; \
    cd /root/vitastor/rpm; \
    sh build-tarball.sh; \
-    cp /root/vitastor-1.2.0.el7.tar.gz ~/rpmbuild/SOURCES; \
+    cp /root/vitastor-1.1.0.el7.tar.gz ~/rpmbuild/SOURCES; \
    cp vitastor-el7.spec ~/rpmbuild/SPECS/vitastor.spec; \
    cd ~/rpmbuild/SPECS/; \
    rpmbuild -ba vitastor.spec; \
--- a/rpm/vitastor-el7.spec
+++ b/rpm/vitastor-el7.spec
@@ -1,11 +1,11 @@
 Name:           vitastor
-Version:        1.2.0
+Version:        1.1.0
 Release:        1%{?dist}
 Summary:        Vitastor, a fast software-defined clustered block storage

 License:        Vitastor Network Public License 1.1
 URL:            https://vitastor.io/
-Source0:        vitastor-1.2.0.el7.tar.gz
+Source0:        vitastor-1.1.0.el7.tar.gz

 BuildRequires:  liburing-devel >= 0.6
 BuildRequires:  gperftools-devel
--- a/rpm/vitastor-el8.Dockerfile
+++ b/rpm/vitastor-el8.Dockerfile
@@ -35,7 +35,7 @@ ADD . /root/vitastor
 RUN set -e; \
    cd /root/vitastor/rpm; \
    sh build-tarball.sh; \
-    cp /root/vitastor-1.2.0.el8.tar.gz ~/rpmbuild/SOURCES; \
+    cp /root/vitastor-1.1.0.el8.tar.gz ~/rpmbuild/SOURCES; \
    cp vitastor-el8.spec ~/rpmbuild/SPECS/vitastor.spec; \
    cd ~/rpmbuild/SPECS/; \
    rpmbuild -ba vitastor.spec; \
--- a/rpm/vitastor-el8.spec
+++ b/rpm/vitastor-el8.spec
@@ -1,11 +1,11 @@
 Name:           vitastor
-Version:        1.2.0
+Version:        1.1.0
 Release:        1%{?dist}
 Summary:        Vitastor, a fast software-defined clustered block storage

 License:        Vitastor Network Public License 1.1
 URL:            https://vitastor.io/
-Source0:        vitastor-1.2.0.el8.tar.gz
+Source0:        vitastor-1.1.0.el8.tar.gz

 BuildRequires:  liburing-devel >= 0.6
 BuildRequires:  gperftools-devel
--- a/rpm/vitastor-el9.Dockerfile
+++ b/rpm/vitastor-el9.Dockerfile
@@ -18,7 +18,7 @@ ADD . /root/vitastor
 RUN set -e; \
    cd /root/vitastor/rpm; \
    sh build-tarball.sh; \
-    cp /root/vitastor-1.2.0.el9.tar.gz ~/rpmbuild/SOURCES; \
+    cp /root/vitastor-1.1.0.el9.tar.gz ~/rpmbuild/SOURCES; \
    cp vitastor-el9.spec ~/rpmbuild/SPECS/vitastor.spec; \
    cd ~/rpmbuild/SPECS/; \
    rpmbuild -ba vitastor.spec; \
--- a/rpm/vitastor-el9.spec
+++ b/rpm/vitastor-el9.spec
@@ -1,11 +1,11 @@
 Name:           vitastor
-Version:        1.2.0
+Version:        1.1.0
 Release:        1%{?dist}
 Summary:        Vitastor, a fast software-defined clustered block storage

 License:        Vitastor Network Public License 1.1
 URL:            https://vitastor.io/
-Source0:        vitastor-1.2.0.el9.tar.gz
+Source0:        vitastor-1.1.0.el9.tar.gz

 BuildRequires:  liburing-devel >= 0.6
 BuildRequires:  gperftools-devel
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -16,11 +16,10 @@ if("${CMAKE_INSTALL_PREFIX}" MATCHES "^/usr/local/?$")
 	set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}")
 endif()

-add_definitions(-DVERSION="1.2.0")
-add_definitions(-Wall -Wno-sign-compare -Wno-comment -Wno-parentheses -Wno-pointer-arith -fdiagnostics-color=always -fno-omit-frame-pointer -I ${CMAKE_SOURCE_DIR}/src)
-add_link_options(-fno-omit-frame-pointer)
+add_definitions(-DVERSION="1.1.0")
+add_definitions(-Wall -Wno-sign-compare -Wno-comment -Wno-parentheses -Wno-pointer-arith -fdiagnostics-color=always -I ${CMAKE_SOURCE_DIR}/src)
 if (${WITH_ASAN})
-	add_definitions(-fsanitize=address)
+	add_definitions(-fsanitize=address -fno-omit-frame-pointer)
 	add_link_options(-fsanitize=address -fno-omit-frame-pointer)
 endif (${WITH_ASAN})

@@ -181,25 +180,6 @@ target_link_libraries(vitastor-nbd
 	vitastor_client
 )

-# vitastor-kv
-add_executable(vitastor-kv
-	kv_cli.cpp
-	kv_db.cpp
-	kv_db.h
-)
-target_link_libraries(vitastor-kv
-	vitastor_client
-)
-
-add_executable(vitastor-kv-stress
-	kv_stress.cpp
-	kv_db.cpp
-	kv_db.h
-)
-target_link_libraries(vitastor-kv-stress
-	vitastor_client
-)
-
 # vitastor-nfs
 add_executable(vitastor-nfs
 	nfs_proxy.cpp
--- a/src/blockstore_flush.cpp
+++ b/src/blockstore_flush.cpp
@@ -1372,8 +1372,7 @@ bool journal_flusher_co::trim_journal(int wait_base)
                    ? (uint32_t)JE_START_V1_SIZE : (uint32_t)JE_START_V2_SIZE),
                .reserved = 0,
                .journal_start = new_trim_pos,
-                .version = (uint64_t)(!bs->dsk.data_csum_type && ((journal_entry_start*)flusher->journal_superblock)->version == JOURNAL_VERSION_V1
-                    ? JOURNAL_VERSION_V1 : JOURNAL_VERSION_V2),
+                .version = JOURNAL_VERSION_V2,
                .data_csum_type = bs->dsk.data_csum_type,
                .csum_block_size = bs->dsk.csum_block_size,
            };
--- a/src/blockstore_impl.h
+++ b/src/blockstore_impl.h
@@ -274,7 +274,7 @@ class blockstore_impl_t
    blockstore_dirty_db_t dirty_db;
    std::vector<blockstore_op_t*> submit_queue;
    std::vector<obj_ver_id> unsynced_big_writes, unsynced_small_writes;
-    int unsynced_big_write_count = 0, unstable_unsynced = 0;
+    int unsynced_big_write_count = 0;
    int unsynced_queued_ops = 0;
    allocator *data_alloc = NULL;
    uint8_t *zero_object;
--- a/src/blockstore_init.cpp
+++ b/src/blockstore_init.cpp
@@ -553,7 +553,7 @@ resume_1:
        }
        if (je_start->size == JE_START_V0_SIZE ||
            (je_start->version != JOURNAL_VERSION_V1 || je_start->size != JE_START_V1_SIZE) &&
-            (je_start->version != JOURNAL_VERSION_V2 || je_start->size != JE_START_V2_SIZE && je_start->size != JE_START_V1_SIZE))
+            (je_start->version != JOURNAL_VERSION_V2 || je_start->size != JE_START_V2_SIZE))
        {
            fprintf(
                stderr, "The code only supports journal versions 2 and 1, but it is %lu on disk."
@@ -562,8 +562,7 @@ resume_1:
            );
            exit(1);
        }
-        if (je_start->version == JOURNAL_VERSION_V1 ||
-            je_start->version == JOURNAL_VERSION_V2 && je_start->size == JE_START_V1_SIZE)
+        if (je_start->version == JOURNAL_VERSION_V1)
        {
            je_start->data_csum_type = 0;
            je_start->csum_block_size = 0;
--- a/src/blockstore_journal.cpp
+++ b/src/blockstore_journal.cpp
@@ -145,7 +145,6 @@ journal_entry* prefill_single_journal_entry(journal_t & journal, uint16_t type,
        journal.sector_info[journal.cur_sector].offset = journal.next_free;
        journal.in_sector_pos = 0;
        journal.next_free = (journal.next_free+journal.block_size) < journal.len ? journal.next_free + journal.block_size : journal.block_size;
-        assert(journal.next_free != journal.used_start);
        memset(journal.inmemory
            ? (uint8_t*)journal.buffer + journal.sector_info[journal.cur_sector].offset
            : (uint8_t*)journal.sector_buf + journal.block_size*journal.cur_sector, 0, journal.block_size);
--- a/src/blockstore_journal.h
+++ b/src/blockstore_journal.h
@@ -13,6 +13,12 @@
 #define JOURNAL_BUFFER_SIZE 4*1024*1024
 #define JOURNAL_ENTRY_HEADER_SIZE 16

+// We reserve some extra space for future stabilize requests during writes
+// FIXME: This value should be dynamic i.e. Blockstore ideally shouldn't allow
+// writing more than can be stabilized afterwards
+#define JOURNAL_STABILIZE_RESERVATION 65536
+#define JOURNAL_INSTANT_RESERVATION 131072
+
 // Journal entries
 // Journal entries are linked to each other by their crc32 value
 // The journal is almost a blockchain, because object versions constantly increase
--- a/src/blockstore_sync.cpp
+++ b/src/blockstore_sync.cpp
@@ -86,15 +86,14 @@ int blockstore_impl_t::continue_sync(blockstore_op_t *op)
                auto & dirty_entry = dirty_db.at(sbw);
                uint64_t dyn_size = dsk.dirty_dyn_size(dirty_entry.offset, dirty_entry.len);
                if (!space_check.check_available(op, 1, sizeof(journal_entry_big_write) + dyn_size,
-                    (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+                    left == 0 ? JOURNAL_STABILIZE_RESERVATION : 0))
                {
                    return 0;
                }
            }
        }
        else if (!space_check.check_available(op, PRIV(op)->sync_big_writes.size(),
-            sizeof(journal_entry_big_write) + dsk.clean_entry_bitmap_size,
-            (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+            sizeof(journal_entry_big_write) + dsk.clean_entry_bitmap_size, JOURNAL_STABILIZE_RESERVATION))
        {
            return 0;
        }
@@ -185,11 +184,6 @@ void blockstore_impl_t::ack_sync(blockstore_op_t *op)
        {
            mark_stable(dirty_it->first);
        }
-        else
-        {
-            unstable_unsynced--;
-            assert(unstable_unsynced >= 0);
-        }
        dirty_it++;
        while (dirty_it != dirty_db.end() && dirty_it->first.oid == it->oid)
        {
@@ -220,11 +214,6 @@ void blockstore_impl_t::ack_sync(blockstore_op_t *op)
            {
                mark_stable(*it);
            }
-            else
-            {
-                unstable_unsynced--;
-                assert(unstable_unsynced >= 0);
-            }
        }
    }
    op->retval = 0;
--- a/src/blockstore_write.cpp
+++ b/src/blockstore_write.cpp
@@ -21,7 +21,7 @@ bool blockstore_impl_t::enqueue_write(blockstore_op_t *op)
        dyn = calloc_or_die(1, dyn_size+sizeof(int));
        *((int*)dyn) = 1;
    }
-    uint8_t *dyn_ptr = (alloc_dyn_data ? (uint8_t*)dyn+sizeof(int) : (uint8_t*)&dyn);
+    uint8_t *dyn_ptr = (uint8_t*)(alloc_dyn_data ? dyn+sizeof(int) : &dyn);
    uint64_t version = 1;
    if (dirty_db.size() > 0)
    {
@@ -320,7 +320,7 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
        blockstore_journal_check_t space_check(this);
        if (!space_check.check_available(op, unsynced_big_write_count + 1,
            sizeof(journal_entry_big_write) + dsk.clean_dyn_size,
-            (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+            (dirty_it->second.state & BS_ST_INSTANT) ? JOURNAL_INSTANT_RESERVATION : JOURNAL_STABILIZE_RESERVATION))
        {
            return 0;
        }
@@ -386,10 +386,6 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
            sqe, dsk.data_fd, PRIV(op)->iov_zerofill, vcnt, dsk.data_offset + (loc << dsk.block_order) + op->offset - stripe_offset
        );
        PRIV(op)->pending_ops = 1;
-        if (immediate_commit != IMMEDIATE_ALL && !(dirty_it->second.state & BS_ST_INSTANT))
-        {
-            unstable_unsynced++;
-        }
        if (immediate_commit != IMMEDIATE_ALL)
        {
            // Increase the counter, but don't save into unsynced_writes yet (can't sync until the write is finished)
@@ -412,7 +408,7 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
                sizeof(journal_entry_big_write) + dsk.clean_dyn_size, 0)
            || !space_check.check_available(op, 1,
                sizeof(journal_entry_small_write) + dyn_size,
-                (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+                op->len + ((dirty_it->second.state & BS_ST_INSTANT) ? JOURNAL_INSTANT_RESERVATION : JOURNAL_STABILIZE_RESERVATION)))
        {
            return 0;
        }
@@ -503,11 +499,6 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
        if (journal.next_free >= journal.len)
        {
            journal.next_free = dsk.journal_block_size;
-            assert(journal.next_free != journal.used_start);
-        }
-        if (immediate_commit == IMMEDIATE_NONE && !(dirty_it->second.state & BS_ST_INSTANT))
-        {
-            unstable_unsynced++;
        }
        if (!PRIV(op)->pending_ops)
        {
@@ -547,7 +538,7 @@ resume_2:
        uint64_t dyn_size = dsk.dirty_dyn_size(op->offset, op->len);
        blockstore_journal_check_t space_check(this);
        if (!space_check.check_available(op, 1, sizeof(journal_entry_big_write) + dyn_size,
-            (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+            ((dirty_it->second.state & BS_ST_INSTANT) ? JOURNAL_INSTANT_RESERVATION : JOURNAL_STABILIZE_RESERVATION)))
        {
            return 0;
        }
@@ -591,20 +582,14 @@ resume_4:
 #endif
        bool is_big = (dirty_it->second.state & BS_ST_TYPE_MASK) == BS_ST_BIG_WRITE;
        bool imm = is_big ? (immediate_commit == IMMEDIATE_ALL) : (immediate_commit != IMMEDIATE_NONE);
-        bool is_instant = ((dirty_it->second.state & BS_ST_TYPE_MASK) == BS_ST_DELETE || (dirty_it->second.state & BS_ST_INSTANT));
        if (imm)
        {
            auto & unstab = unstable_writes[op->oid];
            unstab = unstab < op->version ? op->version : unstab;
        }
-        else if (!is_instant)
-        {
-            unstable_unsynced--;
-            assert(unstable_unsynced >= 0);
-        }
        dirty_it->second.state = (dirty_it->second.state & ~BS_ST_WORKFLOW_MASK)
            | (imm ? BS_ST_SYNCED : BS_ST_WRITTEN);
-        if (imm && is_instant)
+        if (imm && ((dirty_it->second.state & BS_ST_TYPE_MASK) == BS_ST_DELETE || (dirty_it->second.state & BS_ST_INSTANT)))
        {
            // Deletions and 'instant' operations are treated as immediately stable
            mark_stable(dirty_it->first);
@@ -750,7 +735,7 @@ int blockstore_impl_t::dequeue_del(blockstore_op_t *op)
    });
    assert(dirty_it != dirty_db.end());
    blockstore_journal_check_t space_check(this);
-    if (!space_check.check_available(op, 1, sizeof(journal_entry_del), (unstable_writes.size()+unstable_unsynced)*journal.block_size))
+    if (!space_check.check_available(op, 1, sizeof(journal_entry_del), JOURNAL_INSTANT_RESERVATION))
    {
        return 0;
    }
--- a/src/cli.cpp
+++ b/src/cli.cpp
@@ -17,7 +17,7 @@
 static const char *exe_name = NULL;

 static const char* help_text =
-    "Vitastor command-line tool " VERSION "\n"
+    "Vitastor command-line tool\n"
    "(c) Vitaliy Filippov, 2019+ (VNPL-1.1)\n"
    "\n"
    "COMMANDS:\n"
@@ -331,7 +331,7 @@ static int run(cli_tool_t *p, json11::Json::object cfg)
    {
        // Create client
        json11::Json cfg_j = cfg;
-        p->ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+        p->ringloop = new ring_loop_t(512);
        p->epmgr = new epoll_manager_t(p->ringloop);
        p->cli = new cluster_client_t(p->ringloop, p->epmgr->tfd, cfg_j);
        // Smaller timeout by default for more interactiveness
--- a/src/cli_df.cpp
+++ b/src/cli_df.cpp
@@ -109,7 +109,7 @@ resume_1:
            }
            for (auto pg_per_pair: pg_per_osd)
            {
-                uint64_t pg_free = osd_free[pg_per_pair.first] * pool_cfg.real_pg_count / pg_per_pair.second;
+                uint64_t pg_free = osd_free[pg_per_pair.first] * pool_cfg.pg_count / pg_per_pair.second;
                if (pool_avail > pg_free)
                {
                    pool_avail = pg_free;
@@ -127,7 +127,6 @@ resume_1:
                { "id", (uint64_t)pool_cfg.id },
                { "name", pool_cfg.name },
                { "pg_count", pool_cfg.pg_count },
-                { "real_pg_count", pool_cfg.real_pg_count },
                { "scheme", pool_cfg.scheme == POOL_SCHEME_REPLICATED ? "replicated" : "ec" },
                { "scheme_name", pool_cfg.scheme == POOL_SCHEME_REPLICATED
                    ? std::to_string(pool_cfg.pg_size)+"/"+std::to_string(pool_cfg.pg_minsize)
@@ -178,7 +177,7 @@ resume_1:
            { "title", "SCHEME" },
        });
        cols.push_back(json11::Json::object{
-            { "key", "pg_count_fmt" },
+            { "key", "pg_count" },
            { "title", "PGS" },
        });
        cols.push_back(json11::Json::object{
@@ -207,9 +206,6 @@ resume_1:
            double raw_to = kv.second["raw_to_usable"].number_value();
            if (raw_to < 0.000001 && raw_to > -0.000001)
                raw_to = 1;
-            kv.second["pg_count_fmt"] = kv.second["real_pg_count"] == kv.second["pg_count"]
-                ? kv.second["real_pg_count"].as_string()
-                : kv.second["real_pg_count"].as_string()+"->"+kv.second["pg_count"].as_string();
            kv.second["total_fmt"] = format_size(kv.second["total_raw"].uint64_value() / raw_to);
            kv.second["used_fmt"] = format_size(kv.second["used_raw"].uint64_value() / raw_to);
            kv.second["max_avail_fmt"] = format_size(kv.second["max_available"].uint64_value());
--- a/src/cli_status.cpp
+++ b/src/cli_status.cpp
@@ -158,7 +158,12 @@ resume_2:
        for (auto & pool_pair: parent->cli->st_cli.pool_config)
        {
            auto & pool_cfg = pool_pair.second;
-            bool active = pool_cfg.real_pg_count > 0;
+            bool active = true;
+            if (pool_cfg.pg_config.size() != pool_cfg.pg_count)
+            {
+                active = false;
+                pgs_by_state["offline"] += pool_cfg.pg_count-pool_cfg.pg_config.size();
+            }
            pool_count++;
            for (auto pg_it = pool_cfg.pg_config.begin(); pg_it != pool_cfg.pg_config.end(); pg_it++)
            {
--- a/src/cluster_client.cpp
+++ b/src/cluster_client.cpp
@@ -6,7 +6,7 @@
 #include "cluster_client_impl.h"
 #include "http_client.h" // json_is_true

-cluster_client_t::cluster_client_t(ring_loop_t *ringloop, timerfd_manager_t *tfd, json11::Json config)
+cluster_client_t::cluster_client_t(ring_loop_t *ringloop, timerfd_manager_t *tfd, json11::Json & config)
 {
    wb = new writeback_cache_t();

@@ -64,7 +64,7 @@ cluster_client_t::cluster_client_t(ring_loop_t *ringloop, timerfd_manager_t *tfd

 cluster_client_t::~cluster_client_t()
 {
-    msgr.repeer_pgs = [](osd_num_t){};
+    msgr.repeer_pgs = [this](osd_num_t){};
    if (ringloop)
    {
        ringloop->unregister_consumer(&consumer);
@@ -454,7 +454,7 @@ bool cluster_client_t::flush()
            wb->start_writebacks(this, 0);
            cluster_op_t *sync = new cluster_op_t;
            sync->opcode = OSD_OP_SYNC;
-            sync->callback = [](cluster_op_t *sync)
+            sync->callback = [this](cluster_op_t *sync)
            {
                delete sync;
            };
@@ -465,7 +465,7 @@ bool cluster_client_t::flush()
    bool sync_done = false;
    cluster_op_t *sync = new cluster_op_t;
    sync->opcode = OSD_OP_SYNC;
-    sync->callback = [&sync_done](cluster_op_t *sync)
+    sync->callback = [this, &sync_done](cluster_op_t *sync)
    {
        delete sync;
        sync_done = true;
@@ -532,7 +532,7 @@ void cluster_client_t::execute_internal(cluster_op_t *op)
        return;
    }
    if (op->opcode == OSD_OP_WRITE && enable_writeback && !(op->flags & OP_FLUSH_BUFFER) &&
-        !op->version /* no CAS writeback */)
+        !op->version /* FIXME no CAS writeback */)
    {
        if (wb->writebacks_active >= client_max_writeback_iodepth)
        {
@@ -553,7 +553,7 @@ void cluster_client_t::execute_internal(cluster_op_t *op)
    }
    if (op->opcode == OSD_OP_WRITE && !(op->flags & OP_IMMEDIATE_COMMIT))
    {
-        if (!(op->flags & OP_FLUSH_BUFFER) && !op->version /* no CAS write-repeat */)
+        if (!(op->flags & OP_FLUSH_BUFFER))
        {
            wb->copy_write(op, CACHE_WRITTEN);
        }
@@ -1152,7 +1152,7 @@ void cluster_client_t::handle_op_part(cluster_op_part_t *part)
                osd_op_names[part->op.req.hdr.opcode], part->osd_num, part->op.reply.hdr.retval, expected
            );
        }
-        else if (log_level > 0)
+        else
        {
            fprintf(
                stderr, "%s operation failed on OSD %lu: retval=%ld (expected %d)\n",
--- a/src/cluster_client.h
+++ b/src/cluster_client.h
@@ -121,7 +121,7 @@ public:
    json11::Json::object cli_config, file_config, etcd_global_config;
    json11::Json::object config;

-    cluster_client_t(ring_loop_t *ringloop, timerfd_manager_t *tfd, json11::Json config);
+    cluster_client_t(ring_loop_t *ringloop, timerfd_manager_t *tfd, json11::Json & config);
    ~cluster_client_t();
    void execute(cluster_op_t *op);
    void execute_raw(osd_num_t osd_num, osd_op_t *op);
--- a/src/cluster_client_wb.cpp
+++ b/src/cluster_client_wb.cpp
@@ -263,7 +263,7 @@ void writeback_cache_t::flush_buffers(cluster_client_t *cli, dirty_buf_it_t from
    }
    assert(calc_len == op->len);
    writebacks_active++;
-    op->callback = [this, flush_id](cluster_op_t* op)
+    op->callback = [this, cli, flush_id](cluster_op_t* op)
    {
        // Buffer flushes should be always retried, regardless of the error,
        // so they should never result in an error here
@@ -383,7 +383,7 @@ static void copy_to_op(cluster_op_t *op, uint64_t offset, uint8_t *buf, uint64_t
            auto begin = (cur_offset < offset ? offset : cur_offset);
            auto end = (cur_offset+v.iov_len > offset+len ? offset+len : cur_offset+v.iov_len);
            memcpy(
-                (uint8_t*)v.iov_base + begin - cur_offset,
+                v.iov_base + begin - cur_offset,
                buf + (cur_offset <= offset ? 0 : cur_offset-offset),
                end - begin
            );
--- a/src/disk_tool.cpp
+++ b/src/disk_tool.cpp
@@ -5,7 +5,7 @@
 #include "str_util.h"

 static const char *help_text =
-    "Vitastor disk management tool " VERSION "\n"
+    "Vitastor disk management tool\n"
    "(c) Vitaliy Filippov, 2022+ (VNPL-1.1)\n"
    "\n"
    "COMMANDS:\n"
@@ -229,7 +229,7 @@ int main(int argc, char *argv[])
        {
            self.options["allow_data_loss"] = "1";
        }
-        else if (argv[i][0] == '-' && argv[i][1] == '-' && i < argc-1)
+        else if (argv[i][0] == '-' && argv[i][1] == '-')
        {
            char *key = argv[i]+2;
            self.options[key] = argv[++i];
--- a/src/disk_tool_journal.cpp
+++ b/src/disk_tool_journal.cpp
@@ -320,7 +320,7 @@ void disk_tool_t::dump_journal_entry(int num, journal_entry *je, bool json)
        if (journal_calc_data_pos != sw.data_offset)
        {
            printf(json ? ",\"bad_loc\":true,\"calc_loc\":\"0x%lx\""
-                : " (mismatched, calculated = %08lx)", journal_pos);
+                : " (mismatched, calculated = %lu)", journal_pos);
        }
        uint32_t data_csum_size = (!je_start.csum_block_size
            ? 0
--- a/src/disk_tool_resize.cpp
+++ b/src/disk_tool_resize.cpp
@@ -245,7 +245,7 @@ int disk_tool_t::resize_copy_data()
    {
        iodepth = 32;
    }
-    ringloop = new ring_loop_t(iodepth < RINGLOOP_DEFAULT_SIZE ? RINGLOOP_DEFAULT_SIZE : iodepth);
+    ringloop = new ring_loop_t(iodepth < 512 ? 512 : iodepth);
    dsk.data_fd = open(dsk.data_device.c_str(), O_DIRECT|O_RDWR);
    if (dsk.data_fd < 0)
    {
--- a/src/fio_engine.cpp
+++ b/src/fio_engine.cpp
@@ -130,7 +130,7 @@ static int bs_init(struct thread_data *td)
                config[p.first] = p.second.dump();
        }
    }
-    bsd->ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    bsd->ringloop = new ring_loop_t(512);
    bsd->epmgr = new epoll_manager_t(bsd->ringloop);
    bsd->bs = new blockstore_t(config, bsd->ringloop, bsd->epmgr->tfd);
    while (1)
--- a/src/kv_cli.cpp
+++ b/src/kv_cli.cpp
@@ -1,401 +0,0 @@
-// Copyright (c) Vitaliy Filippov, 2019+
-// License: VNPL-1.1 (see README.md for details)
-//
-// Vitastor shared key/value database test CLI
-
-#define _XOPEN_SOURCE
-#include <limits.h>
-
-#include <netinet/tcp.h>
-#include <sys/epoll.h>
-#include <unistd.h>
-#include <fcntl.h>
-//#include <signal.h>
-
-#include "epoll_manager.h"
-#include "str_util.h"
-#include "kv_db.h"
-
-const char *exe_name = NULL;
-
-class kv_cli_t
-{
-public:
-    kv_dbw_t *db = NULL;
-    ring_loop_t *ringloop = NULL;
-    epoll_manager_t *epmgr = NULL;
-    cluster_client_t *cli = NULL;
-    bool interactive = false;
-    int in_progress = 0;
-    char *cur_cmd = NULL;
-    int cur_cmd_size = 0, cur_cmd_alloc = 0;
-    bool finished = false, eof = false;
-    json11::Json::object cfg;
-
-    ~kv_cli_t();
-
-    static json11::Json::object parse_args(int narg, const char *args[]);
-    void run(const json11::Json::object & cfg);
-    void read_cmd();
-    void next_cmd();
-    void handle_cmd(const std::string & cmd, std::function<void()> cb);
-};
-
-kv_cli_t::~kv_cli_t()
-{
-    if (cur_cmd)
-    {
-        free(cur_cmd);
-        cur_cmd = NULL;
-    }
-    cur_cmd_alloc = 0;
-    if (db)
-        delete db;
-    if (cli)
-    {
-        cli->flush();
-        delete cli;
-    }
-    if (epmgr)
-        delete epmgr;
-    if (ringloop)
-        delete ringloop;
-}
-
-json11::Json::object kv_cli_t::parse_args(int narg, const char *args[])
-{
-    json11::Json::object cfg;
-    for (int i = 1; i < narg; i++)
-    {
-        if (!strcmp(args[i], "-h") || !strcmp(args[i], "--help"))
-        {
-            printf(
-                "Vitastor Key/Value CLI\n"
-                "(c) Vitaliy Filippov, 2023+ (VNPL-1.1)\n"
-                "\n"
-                "USAGE: %s [--etcd_address ADDR] [OTHER OPTIONS]\n",
-                exe_name
-            );
-            exit(0);
-        }
-        else if (args[i][0] == '-' && args[i][1] == '-')
-        {
-            const char *opt = args[i]+2;
-            cfg[opt] = !strcmp(opt, "json") || i == narg-1 ? "1" : args[++i];
-        }
-    }
-    return cfg;
-}
-
-void kv_cli_t::run(const json11::Json::object & cfg)
-{
-    // Create client
-    ringloop = new ring_loop_t(512);
-    epmgr = new epoll_manager_t(ringloop);
-    cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
-    db = new kv_dbw_t(cli);
-    // Load image metadata
-    while (!cli->is_ready())
-    {
-        ringloop->loop();
-        if (cli->is_ready())
-            break;
-        ringloop->wait();
-    }
-    // Run
-    fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
-    try
-    {
-        epmgr->tfd->set_fd_handler(0, false, [this](int fd, int events)
-        {
-            if (events & EPOLLIN)
-            {
-                read_cmd();
-            }
-            if (events & EPOLLRDHUP)
-            {
-                epmgr->tfd->set_fd_handler(0, false, NULL);
-                finished = true;
-            }
-        });
-        interactive = true;
-        printf("> ");
-    }
-    catch (std::exception & e)
-    {
-        // Can't add to epoll, STDIN is probably a file
-        read_cmd();
-    }
-    while (!finished)
-    {
-        ringloop->loop();
-        if (!finished)
-            ringloop->wait();
-    }
-    // Destroy the client
-    delete db;
-    db = NULL;
-    cli->flush();
-    delete cli;
-    delete epmgr;
-    delete ringloop;
-    cli = NULL;
-    epmgr = NULL;
-    ringloop = NULL;
-}
-
-void kv_cli_t::read_cmd()
-{
-    if (!cur_cmd_alloc)
-    {
-        cur_cmd_alloc = 65536;
-        cur_cmd = (char*)malloc_or_die(cur_cmd_alloc);
-    }
-    while (cur_cmd_size < cur_cmd_alloc)
-    {
-        int r = read(0, cur_cmd+cur_cmd_size, cur_cmd_alloc-cur_cmd_size);
-        if (r < 0 && errno != EAGAIN)
-            fprintf(stderr, "Error reading from stdin: %s\n", strerror(errno));
-        if (r > 0)
-            cur_cmd_size += r;
-        if (r == 0)
-            eof = true;
-        if (r <= 0)
-            break;
-    }
-    next_cmd();
-}
-
-void kv_cli_t::next_cmd()
-{
-    if (in_progress > 0)
-    {
-        return;
-    }
-    int pos = 0;
-    for (; pos < cur_cmd_size; pos++)
-    {
-        if (cur_cmd[pos] == '\n' || cur_cmd[pos] == '\r')
-        {
-            auto cmd = trim(std::string(cur_cmd, pos));
-            pos++;
-            memmove(cur_cmd, cur_cmd+pos, cur_cmd_size-pos);
-            cur_cmd_size -= pos;
-            in_progress++;
-            handle_cmd(cmd, [this]()
-            {
-                in_progress--;
-                if (interactive)
-                    printf("> ");
-                next_cmd();
-                if (!in_progress)
-                    read_cmd();
-            });
-            break;
-        }
-    }
-    if (eof && !in_progress)
-    {
-        finished = true;
-    }
-}
-
-void kv_cli_t::handle_cmd(const std::string & cmd, std::function<void()> cb)
-{
-    if (cmd == "")
-    {
-        cb();
-        return;
-    }
-    auto pos = cmd.find_first_of(" \t");
-    if (pos != std::string::npos)
-    {
-        while (pos < cmd.size()-1 && (cmd[pos+1] == ' ' || cmd[pos+1] == '\t'))
-            pos++;
-    }
-    auto opname = strtolower(pos == std::string::npos ? cmd : cmd.substr(0, pos));
-    if (opname == "open")
-    {
-        uint64_t pool_id = 0;
-        inode_t inode_id = 0;
-        uint32_t kv_block_size = 0;
-        int scanned = sscanf(cmd.c_str() + pos+1, "%lu %lu %u", &pool_id, &inode_id, &kv_block_size);
-        if (scanned == 2)
-        {
-            kv_block_size = 4096;
-        }
-        if (scanned < 2 || !pool_id || !inode_id || !kv_block_size || (kv_block_size & (kv_block_size-1)) != 0)
-        {
-            fprintf(stderr, "Usage: open <pool_id> <inode_id> [block_size]. Block size must be a power of 2. Default is 4096.\n");
-            cb();
-            return;
-        }
-        cfg["kv_block_size"] = (uint64_t)kv_block_size;
-        db->open(INODE_WITH_POOL(pool_id, inode_id), cfg, [=](int res)
-        {
-            if (res < 0)
-                fprintf(stderr, "Error opening index: %s (code %d)\n", strerror(-res), res);
-            else
-                printf("Index opened. Current size: %lu bytes\n", db->get_size());
-            cb();
-        });
-    }
-    else if (opname == "config")
-    {
-        auto pos2 = cmd.find_first_of(" \t", pos+1);
-        if (pos2 == std::string::npos)
-        {
-            fprintf(stderr, "Usage: config <property> <value>\n");
-            cb();
-            return;
-        }
-        auto key = trim(cmd.substr(pos+1, pos2-pos-1));
-        auto value = parse_size(trim(cmd.substr(pos2+1)));
-        if (key != "kv_memory_limit" &&
-            key != "kv_allocate_blocks" &&
-            key != "kv_evict_max_misses" &&
-            key != "kv_evict_attempts_per_level" &&
-            key != "kv_evict_unused_age" &&
-            key != "kv_log_level")
-        {
-            fprintf(
-                stderr, "Allowed properties: kv_memory_limit, kv_allocate_blocks,"
-                " kv_evict_max_misses, kv_evict_attempts_per_level, kv_evict_unused_age, kv_log_level\n"
-            );
-        }
-        else
-        {
-            cfg[key] = value;
-            db->set_config(cfg);
-        }
-        cb();
-    }
-    else if (opname == "get" || opname == "set" || opname == "del")
-    {
-        if (opname == "get" || opname == "del")
-        {
-            if (pos == std::string::npos)
-            {
-                fprintf(stderr, "Usage: %s <key>\n", opname.c_str());
-                cb();
-                return;
-            }
-            auto key = trim(cmd.substr(pos+1));
-            if (opname == "get")
-            {
-                db->get(key, [this, cb](int res, const std::string & value)
-                {
-                    if (res < 0)
-                        fprintf(stderr, "Error: %s (code %d)\n", strerror(-res), res);
-                    else
-                    {
-                        write(1, value.c_str(), value.size());
-                        write(1, "\n", 1);
-                    }
-                    cb();
-                });
-            }
-            else
-            {
-                db->del(key, [this, cb](int res)
-                {
-                    if (res < 0)
-                        fprintf(stderr, "Error: %s (code %d)\n", strerror(-res), res);
-                    else
-                        printf("OK\n");
-                    cb();
-                });
-            }
-        }
-        else
-        {
-            auto pos2 = cmd.find_first_of(" \t", pos+1);
-            if (pos2 == std::string::npos)
-            {
-                fprintf(stderr, "Usage: set <key> <value>\n");
-                cb();
-                return;
-            }
-            auto key = trim(cmd.substr(pos+1, pos2-pos-1));
-            auto value = trim(cmd.substr(pos2+1));
-            db->set(key, value, [this, cb](int res)
-            {
-                if (res < 0)
-                    fprintf(stderr, "Error: %s (code %d)\n", strerror(-res), res);
-                else
-                    printf("OK\n");
-                cb();
-            });
-        }
-    }
-    else if (opname == "list")
-    {
-        std::string start, end;
-        if (pos != std::string::npos)
-        {
-            auto pos2 = cmd.find_first_of(" \t", pos+1);
-            if (pos2 != std::string::npos)
-            {
-                start = trim(cmd.substr(pos+1, pos2-pos-1));
-                end = trim(cmd.substr(pos2+1));
-            }
-            else
-            {
-                start = trim(cmd.substr(pos+1));
-            }
-        }
-        void *handle = db->list_start(start);
-        db->list_next(handle, [=](int res, const std::string & key, const std::string & value)
-        {
-            if (res < 0)
-            {
-                if (res != -ENOENT)
-                {
-                    fprintf(stderr, "Error: %s (code %d)\n", strerror(-res), res);
-                }
-                db->list_close(handle);
-                cb();
-            }
-            else
-            {
-                printf("%s = %s\n", key.c_str(), value.c_str());
-                db->list_next(handle, NULL);
-            }
-        });
-    }
-    else if (opname == "close")
-    {
-        db->close([=]()
-        {
-            printf("Index closed\n");
-            cb();
-        });
-    }
-    else if (opname == "quit" || opname == "q")
-    {
-        ::close(0);
-        finished = true;
-    }
-    else
-    {
-        fprintf(
-            stderr, "Unknown operation: %s. Supported operations:\n"
-            "open <pool_id> <inode_id> [block_size]\n"
-            "config <property> <value>\n"
-            "get <key>\nset <key> <value>\ndel <key>\nlist [<start> [end]]\n"
-            "close\nquit\n", opname.c_str()
-        );
-        cb();
-    }
-}
-
-int main(int narg, const char *args[])
-{
-    setvbuf(stdout, NULL, _IONBF, 0);
-    setvbuf(stderr, NULL, _IONBF, 0);
-    exe_name = args[0];
-    kv_cli_t *p = new kv_cli_t();
-    p->run(kv_cli_t::parse_args(narg, args));
-    delete p;
-    return 0;
-}
--- a/src/kv_db.cpp
+++ b/src/kv_db.cpp
--- a/src/kv_db.h
+++ b/src/kv_db.h
@@ -1,36 +0,0 @@
-// Copyright (c) Vitaliy Filippov, 2019+
-// License: VNPL-1.1 (see README.md for details)
-//
-// Vitastor shared key/value database
-// Parallel optimistic B-Tree O:-)
-
-#pragma once
-
-#include "cluster_client.h"
-
-struct kv_db_t;
-
-struct kv_dbw_t
-{
-    kv_dbw_t(cluster_client_t *cli);
-    ~kv_dbw_t();
-
-    void open(inode_t inode_id, json11::Json cfg, std::function<void(int)> cb);
-    void set_config(json11::Json cfg);
-    void close(std::function<void()> cb);
-
-    uint64_t get_size();
-
-    void get(const std::string & key, std::function<void(int res, const std::string & value)> cb,
-        bool allow_old_cached = false);
-    void set(const std::string & key, const std::string & value, std::function<void(int res)> cb,
-        std::function<bool(int res, const std::string & value)> cas_compare = NULL);
-    void del(const std::string & key, std::function<void(int res)> cb,
-        std::function<bool(int res, const std::string & value)> cas_compare = NULL);
-
-    void* list_start(const std::string & start);
-    void list_next(void *handle, std::function<void(int res, const std::string & key, const std::string & value)> cb);
-    void list_close(void *handle);
-
-    kv_db_t *db;
-};
--- a/src/kv_stress.cpp
+++ b/src/kv_stress.cpp
@@ -1,697 +0,0 @@
-// Copyright (c) Vitaliy Filippov, 2019+
-// License: VNPL-1.1 (see README.md for details)
-//
-// Vitastor shared key/value database stress tester / benchmark
-
-#define _XOPEN_SOURCE
-#include <limits.h>
-
-#include <netinet/tcp.h>
-#include <sys/epoll.h>
-#include <unistd.h>
-#include <fcntl.h>
-//#include <signal.h>
-
-#include "epoll_manager.h"
-#include "str_util.h"
-#include "kv_db.h"
-
-const char *exe_name = NULL;
-
-struct kv_test_listing_t
-{
-    uint64_t count = 0, done = 0;
-    void *handle = NULL;
-    std::string next_after;
-    std::set<std::string> inflights;
-    timespec tv_begin;
-    bool error = false;
-};
-
-struct kv_test_lat_t
-{
-    const char *name = NULL;
-    uint64_t usec = 0, count = 0;
-};
-
-struct kv_test_stat_t
-{
-    kv_test_lat_t get, add, update, del, list;
-    uint64_t list_keys = 0;
-};
-
-class kv_test_t
-{
-public:
-    // Config
-    json11::Json::object kv_cfg;
-    std::string key_prefix, key_suffix;
-    uint64_t inode_id = 0;
-    uint64_t op_count = 1000000;
-    uint64_t runtime_sec = 0;
-    uint64_t parallelism = 4;
-    uint64_t reopen_prob = 1;
-    uint64_t get_prob = 30000;
-    uint64_t add_prob = 20000;
-    uint64_t update_prob = 20000;
-    uint64_t del_prob = 5000;
-    uint64_t list_prob = 300;
-    uint64_t min_key_len = 10;
-    uint64_t max_key_len = 70;
-    uint64_t min_value_len = 50;
-    uint64_t max_value_len = 300;
-    uint64_t min_list_count = 10;
-    uint64_t max_list_count = 1000;
-    uint64_t print_stats_interval = 1;
-    bool json_output = false;
-    uint64_t log_level = 1;
-    bool trace = false;
-    bool stop_on_error = false;
-    // FIXME: Multiple clients
-    kv_test_stat_t stat, prev_stat;
-    timespec prev_stat_time, start_stat_time;
-
-    // State
-    kv_dbw_t *db = NULL;
-    ring_loop_t *ringloop = NULL;
-    epoll_manager_t *epmgr = NULL;
-    cluster_client_t *cli = NULL;
-    ring_consumer_t consumer;
-    bool finished = false;
-    uint64_t total_prob = 0;
-    uint64_t ops_sent = 0, ops_done = 0;
-    int stat_timer_id = -1;
-    int in_progress = 0;
-    bool reopening = false;
-    std::set<kv_test_listing_t*> listings;
-    std::set<std::string> changing_keys;
-    std::map<std::string, std::string> values;
-
-    ~kv_test_t();
-
-    static json11::Json::object parse_args(int narg, const char *args[]);
-    void parse_config(json11::Json cfg);
-    void run(json11::Json cfg);
-    void loop();
-    void print_stats(kv_test_stat_t & prev_stat, timespec & prev_stat_time);
-    void print_total_stats();
-    void start_change(const std::string & key);
-    void stop_change(const std::string & key);
-    void add_stat(kv_test_lat_t & stat, timespec tv_begin);
-};
-
-kv_test_t::~kv_test_t()
-{
-    if (db)
-        delete db;
-    if (cli)
-    {
-        cli->flush();
-        delete cli;
-    }
-    if (epmgr)
-        delete epmgr;
-    if (ringloop)
-        delete ringloop;
-}
-
-json11::Json::object kv_test_t::parse_args(int narg, const char *args[])
-{
-    json11::Json::object cfg;
-    for (int i = 1; i < narg; i++)
-    {
-        if (!strcmp(args[i], "-h") || !strcmp(args[i], "--help"))
-        {
-            printf(
-                "Vitastor Key/Value DB stress tester / benchmark\n"
-                "(c) Vitaliy Filippov, 2023+ (VNPL-1.1)\n"
-                "\n"
-                "USAGE: %s --pool_id POOL_ID --inode_id INODE_ID [OPTIONS]\n"
-                "  --op_count 1000000\n"
-                "    Total operations to run during test. 0 means unlimited\n"
-                "  --key_prefix \"\"\n"
-                "    Prefix for all keys read or written (to avoid collisions)\n"
-                "  --key_suffix \"\"\n"
-                "    Suffix for all keys read or written (to avoid collisions, but scan all DB)\n"
-                "  --runtime 0\n"
-                "    Run for this number of seconds. 0 means unlimited\n"
-                "  --parallelism 4\n"
-                "    Run this number of operations in parallel\n"
-                "  --get_prob 30000\n"
-                "    Fraction of key retrieve operations\n"
-                "  --add_prob 20000\n"
-                "    Fraction of key addition operations\n"
-                "  --update_prob 20000\n"
-                "    Fraction of key update operations\n"
-                "  --del_prob 30000\n"
-                "    Fraction of key delete operations\n"
-                "  --list_prob 300\n"
-                "    Fraction of listing operations\n"
-                "  --min_key_len 10\n"
-                "    Minimum key size in bytes\n"
-                "  --max_key_len 70\n"
-                "    Maximum key size in bytes\n"
-                "  --min_value_len 50\n"
-                "    Minimum value size in bytes\n"
-                "  --max_value_len 300\n"
-                "    Maximum value size in bytes\n"
-                "  --min_list_count 10\n"
-                "    Minimum number of keys read in listing (0 = all keys)\n"
-                "  --max_list_count 1000\n"
-                "    Maximum number of keys read in listing\n"
-                "  --print_stats 1\n"
-                "    Print operation statistics every this number of seconds\n"
-                "  --json\n"
-                "    JSON output\n"
-                "  --stop_on_error 0\n"
-                "    Stop on first execution error, mismatch, lost key or extra key during listing\n"
-                "  --kv_memory_limit 128M\n"
-                "    Maximum memory to use for vitastor-kv index cache\n"
-                "  --kv_allocate_blocks 4\n"
-                "    Number of PG blocks used for new tree block allocation in parallel\n"
-                "  --kv_evict_max_misses 10\n"
-                "    Eviction algorithm parameter: retry eviction from another random spot\n"
-                "    if this number of keys is used currently or was used recently\n"
-                "  --kv_evict_attempts_per_level 3\n"
-                "    Retry eviction at most this number of times per tree level, starting\n"
-                "    with bottom-most levels\n"
-                "  --kv_evict_unused_age 1000\n"
-                "    Evict only keys unused during this number of last operations\n"
-                "  --kv_log_level 1\n"
-                "    Log level. 0 = errors, 1 = warnings, 10 = trace operations\n",
-                exe_name
-            );
-            exit(0);
-        }
-        else if (args[i][0] == '-' && args[i][1] == '-')
-        {
-            const char *opt = args[i]+2;
-            cfg[opt] = !strcmp(opt, "json") || i == narg-1 ? "1" : args[++i];
-        }
-    }
-    return cfg;
-}
-
-void kv_test_t::parse_config(json11::Json cfg)
-{
-    inode_id = INODE_WITH_POOL(cfg["pool_id"].uint64_value(), cfg["inode_id"].uint64_value());
-    if (cfg["op_count"].uint64_value() > 0)
-        op_count = cfg["op_count"].uint64_value();
-    key_prefix = cfg["key_prefix"].string_value();
-    key_suffix = cfg["key_suffix"].string_value();
-    if (cfg["runtime"].uint64_value() > 0)
-        runtime_sec = cfg["runtime"].uint64_value();
-    if (cfg["parallelism"].uint64_value() > 0)
-        parallelism = cfg["parallelism"].uint64_value();
-    if (!cfg["reopen_prob"].is_null())
-        reopen_prob = cfg["reopen_prob"].uint64_value();
-    if (!cfg["get_prob"].is_null())
-        get_prob = cfg["get_prob"].uint64_value();
-    if (!cfg["add_prob"].is_null())
-        add_prob = cfg["add_prob"].uint64_value();
-    if (!cfg["update_prob"].is_null())
-        update_prob = cfg["update_prob"].uint64_value();
-    if (!cfg["del_prob"].is_null())
-        del_prob = cfg["del_prob"].uint64_value();
-    if (!cfg["list_prob"].is_null())
-        list_prob = cfg["list_prob"].uint64_value();
-    if (!cfg["min_key_len"].is_null())
-        min_key_len = cfg["min_key_len"].uint64_value();
-    if (cfg["max_key_len"].uint64_value() > 0)
-        max_key_len = cfg["max_key_len"].uint64_value();
-    if (!cfg["min_value_len"].is_null())
-        min_value_len = cfg["min_value_len"].uint64_value();
-    if (cfg["max_value_len"].uint64_value() > 0)
-        max_value_len = cfg["max_value_len"].uint64_value();
-    if (!cfg["min_list_count"].is_null())
-        min_list_count = cfg["min_list_count"].uint64_value();
-    if (!cfg["max_list_count"].is_null())
-        max_list_count = cfg["max_list_count"].uint64_value();
-    if (!cfg["print_stats"].is_null())
-        print_stats_interval = cfg["print_stats"].uint64_value();
-    if (!cfg["json"].is_null())
-        json_output = true;
-    if (!cfg["stop_on_error"].is_null())
-        stop_on_error = cfg["stop_on_error"].bool_value();
-    if (!cfg["kv_memory_limit"].is_null())
-        kv_cfg["kv_memory_limit"] = cfg["kv_memory_limit"];
-    if (!cfg["kv_allocate_blocks"].is_null())
-        kv_cfg["kv_allocate_blocks"] = cfg["kv_allocate_blocks"];
-    if (!cfg["kv_evict_max_misses"].is_null())
-        kv_cfg["kv_evict_max_misses"] = cfg["kv_evict_max_misses"];
-    if (!cfg["kv_evict_attempts_per_level"].is_null())
-        kv_cfg["kv_evict_attempts_per_level"] = cfg["kv_evict_attempts_per_level"];
-    if (!cfg["kv_evict_unused_age"].is_null())
-        kv_cfg["kv_evict_unused_age"] = cfg["kv_evict_unused_age"];
-    if (!cfg["kv_log_level"].is_null())
-    {
-        log_level = cfg["kv_log_level"].uint64_value();
-        trace = log_level >= 10;
-        kv_cfg["kv_log_level"] = cfg["kv_log_level"];
-    }
-    total_prob = reopen_prob+get_prob+add_prob+update_prob+del_prob+list_prob;
-    stat.get.name = "get";
-    stat.add.name = "add";
-    stat.update.name = "update";
-    stat.del.name = "del";
-    stat.list.name = "list";
-}
-
-void kv_test_t::run(json11::Json cfg)
-{
-    srand48(time(NULL));
-    parse_config(cfg);
-    // Create client
-    ringloop = new ring_loop_t(512);
-    epmgr = new epoll_manager_t(ringloop);
-    cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
-    db = new kv_dbw_t(cli);
-    // Load image metadata
-    while (!cli->is_ready())
-    {
-        ringloop->loop();
-        if (cli->is_ready())
-            break;
-        ringloop->wait();
-    }
-    // Run
-    reopening = true;
-    db->open(inode_id, kv_cfg, [this](int res)
-    {
-        reopening = false;
-        if (res < 0)
-        {
-            fprintf(stderr, "ERROR: Open index: %d (%s)\n", res, strerror(-res));
-            exit(1);
-        }
-        if (trace)
-            printf("Index opened\n");
-        ringloop->wakeup();
-    });
-    consumer.loop = [this]() { loop(); };
-    ringloop->register_consumer(&consumer);
-    if (print_stats_interval)
-        stat_timer_id = epmgr->tfd->set_timer(print_stats_interval*1000, true, [this](int) { print_stats(prev_stat, prev_stat_time); });
-    clock_gettime(CLOCK_REALTIME, &start_stat_time);
-    prev_stat_time = start_stat_time;
-    while (!finished)
-    {
-        ringloop->loop();
-        if (!finished)
-            ringloop->wait();
-    }
-    if (stat_timer_id >= 0)
-        epmgr->tfd->clear_timer(stat_timer_id);
-    ringloop->unregister_consumer(&consumer);
-    // Print total stats
-    print_total_stats();
-    // Destroy the client
-    delete db;
-    db = NULL;
-    cli->flush();
-    delete cli;
-    delete epmgr;
-    delete ringloop;
-    cli = NULL;
-    epmgr = NULL;
-    ringloop = NULL;
-}
-
-static const char *base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@+/";
-
-std::string random_str(int len)
-{
-    std::string str;
-    str.resize(len);
-    for (int i = 0; i < len; i++)
-    {
-        str[i] = base64_chars[lrand48() % 64];
-    }
-    return str;
-}
-
-void kv_test_t::loop()
-{
-    if (reopening)
-    {
-        return;
-    }
-    if (ops_done >= op_count)
-    {
-        finished = true;
-    }
-    while (!finished && ops_sent < op_count && in_progress < parallelism)
-    {
-        uint64_t dice = (lrand48() % total_prob);
-        if (dice < reopen_prob)
-        {
-            reopening = true;
-            db->close([this]()
-            {
-                if (trace)
-                    printf("Index closed\n");
-                db->open(inode_id, kv_cfg, [this](int res)
-                {
-                    reopening = false;
-                    if (res < 0)
-                    {
-                        fprintf(stderr, "ERROR: Reopen index: %d (%s)\n", res, strerror(-res));
-                        finished = true;
-                        return;
-                    }
-                    if (trace)
-                        printf("Index reopened\n");
-                    ringloop->wakeup();
-                });
-            });
-            return;
-        }
-        else if (dice < reopen_prob+get_prob)
-        {
-            // get existing
-            auto key = random_str(max_key_len);
-            auto k_it = values.lower_bound(key);
-            if (k_it == values.end())
-                continue;
-            key = k_it->first;
-            if (changing_keys.find(key) != changing_keys.end())
-                continue;
-            in_progress++;
-            ops_sent++;
-            if (trace)
-                printf("get %s\n", key.c_str());
-            timespec tv_begin;
-            clock_gettime(CLOCK_REALTIME, &tv_begin);
-            db->get(key, [this, key, tv_begin](int res, const std::string & value)
-            {
-                add_stat(stat.get, tv_begin);
-                ops_done++;
-                in_progress--;
-                auto it = values.find(key);
-                if (res != (it == values.end() ? -ENOENT : 0))
-                {
-                    fprintf(stderr, "ERROR: get %s: %d (%s)\n", key.c_str(), res, strerror(-res));
-                    if (stop_on_error)
-                        exit(1);
-                }
-                else if (it != values.end() && value != it->second)
-                {
-                    fprintf(stderr, "ERROR: get %s: mismatch: %s vs %s\n", key.c_str(), value.c_str(), it->second.c_str());
-                    if (stop_on_error)
-                        exit(1);
-                }
-                ringloop->wakeup();
-            });
-        }
-        else if (dice < reopen_prob+get_prob+add_prob+update_prob)
-        {
-            bool is_add = false;
-            std::string key;
-            if (dice < reopen_prob+get_prob+add_prob)
-            {
-                // add
-                is_add = true;
-                uint64_t key_len = min_key_len + (max_key_len > min_key_len ? lrand48() % (max_key_len-min_key_len) : 0);
-                key = key_prefix + random_str(key_len) + key_suffix;
-            }
-            else
-            {
-                // update
-                key = random_str(max_key_len);
-                auto k_it = values.lower_bound(key);
-                if (k_it == values.end())
-                    continue;
-                key = k_it->first;
-            }
-            if (changing_keys.find(key) != changing_keys.end())
-                continue;
-            uint64_t value_len = min_value_len + (max_value_len > min_value_len ? lrand48() % (max_value_len-min_value_len) : 0);
-            auto value = random_str(value_len);
-            start_change(key);
-            ops_sent++;
-            in_progress++;
-            if (trace)
-                printf("set %s = %s\n", key.c_str(), value.c_str());
-            timespec tv_begin;
-            clock_gettime(CLOCK_REALTIME, &tv_begin);
-            db->set(key, value, [this, key, value, tv_begin, is_add](int res)
-            {
-                add_stat(is_add ? stat.add : stat.update, tv_begin);
-                stop_change(key);
-                ops_done++;
-                in_progress--;
-                if (res != 0)
-                {
-                    fprintf(stderr, "ERROR: set %s = %s: %d (%s)\n", key.c_str(), value.c_str(), res, strerror(-res));
-                    if (stop_on_error)
-                        exit(1);
-                }
-                else
-                {
-                    values[key] = value;
-                }
-                ringloop->wakeup();
-            }, NULL);
-        }
-        else if (dice < reopen_prob+get_prob+add_prob+update_prob+del_prob)
-        {
-            // delete
-            auto key = random_str(max_key_len);
-            auto k_it = values.lower_bound(key);
-            if (k_it == values.end())
-                continue;
-            key = k_it->first;
-            if (changing_keys.find(key) != changing_keys.end())
-                continue;
-            start_change(key);
-            ops_sent++;
-            in_progress++;
-            if (trace)
-                printf("del %s\n", key.c_str());
-            timespec tv_begin;
-            clock_gettime(CLOCK_REALTIME, &tv_begin);
-            db->del(key, [this, key, tv_begin](int res)
-            {
-                add_stat(stat.del, tv_begin);
-                stop_change(key);
-                ops_done++;
-                in_progress--;
-                if (res != 0)
-                {
-                    fprintf(stderr, "ERROR: del %s: %d (%s)\n", key.c_str(), res, strerror(-res));
-                    if (stop_on_error)
-                        exit(1);
-                }
-                else
-                {
-                    values.erase(key);
-                }
-                ringloop->wakeup();
-            }, NULL);
-        }
-        else if (dice < reopen_prob+get_prob+add_prob+update_prob+del_prob+list_prob)
-        {
-            // list
-            ops_sent++;
-            in_progress++;
-            auto key = random_str(max_key_len);
-            auto lst = new kv_test_listing_t;
-            auto k_it = values.lower_bound(key);
-            lst->count = min_list_count + (max_list_count > min_list_count ? lrand48() % (max_list_count-min_list_count) : 0);
-            lst->handle = db->list_start(k_it == values.begin() ? key_prefix : key);
-            lst->next_after = k_it == values.begin() ? key_prefix : key;
-            lst->inflights = changing_keys;
-            listings.insert(lst);
-            if (trace)
-                printf("list from %s\n", key.c_str());
-            clock_gettime(CLOCK_REALTIME, &lst->tv_begin);
-            db->list_next(lst->handle, [this, lst](int res, const std::string & key, const std::string & value)
-            {
-                if (log_level >= 11)
-                    printf("list: %s = %s\n", key.c_str(), value.c_str());
-                if (res >= 0 && key_prefix.size() && (key.size() < key_prefix.size() ||
-                    key.substr(0, key_prefix.size()) != key_prefix))
-                {
-                    // stop at this key
-                    res = -ENOENT;
-                }
-                if (res < 0 || (lst->count > 0 && lst->done >= lst->count))
-                {
-                    add_stat(stat.list, lst->tv_begin);
-                    if (res == 0)
-                    {
-                        // ok (done >= count)
-                    }
-                    else if (res != -ENOENT)
-                    {
-                        fprintf(stderr, "ERROR: list: %d (%s)\n", res, strerror(-res));
-                        lst->error = true;
-                    }
-                    else
-                    {
-                        auto k_it = lst->next_after == "" ? values.begin() : values.upper_bound(lst->next_after);
-                        while (k_it != values.end())
-                        {
-                            while (k_it != values.end() && lst->inflights.find(k_it->first) != lst->inflights.end())
-                                k_it++;
-                            if (k_it != values.end())
-                            {
-                                fprintf(stderr, "ERROR: list: missing key %s\n", (k_it++)->first.c_str());
-                                lst->error = true;
-                            }
-                        }
-                    }
-                    if (lst->error && stop_on_error)
-                        exit(1);
-                    ops_done++;
-                    in_progress--;
-                    db->list_close(lst->handle);
-                    delete lst;
-                    listings.erase(lst);
-                    ringloop->wakeup();
-                }
-                else
-                {
-                    stat.list_keys++;
-                    // Do not check modified keys in listing
-                    // Listing may return their old or new state
-                    if ((!key_suffix.size() || key.size() >= key_suffix.size() &&
-                        key.substr(key.size()-key_suffix.size()) == key_suffix) &&
-                        lst->inflights.find(key) == lst->inflights.end())
-                    {
-                        lst->done++;
-                        auto k_it = lst->next_after == "" ? values.begin() : values.upper_bound(lst->next_after);
-                        while (true)
-                        {
-                            while (k_it != values.end() && lst->inflights.find(k_it->first) != lst->inflights.end())
-                            {
-                                k_it++;
-                            }
-                            if (k_it == values.end() || k_it->first > key)
-                            {
-                                fprintf(stderr, "ERROR: list: extra key %s\n", key.c_str());
-                                lst->error = true;
-                                break;
-                            }
-                            else if (k_it->first < key)
-                            {
-                                fprintf(stderr, "ERROR: list: missing key %s\n", k_it->first.c_str());
-                                lst->error = true;
-                                lst->next_after = k_it->first;
-                                k_it++;
-                            }
-                            else
-                            {
-                                if (k_it->second != value)
-                                {
-                                    fprintf(stderr, "ERROR: list: mismatch: %s = %s but should be %s\n",
-                                        key.c_str(), value.c_str(), k_it->second.c_str());
-                                    lst->error = true;
-                                }
-                                lst->next_after = k_it->first;
-                                break;
-                            }
-                        }
-                    }
-                    db->list_next(lst->handle, NULL);
-                }
-            });
-        }
-    }
-}
-
-void kv_test_t::add_stat(kv_test_lat_t & stat, timespec tv_begin)
-{
-    timespec tv_end;
-    clock_gettime(CLOCK_REALTIME, &tv_end);
-    int64_t usec = (tv_end.tv_sec - tv_begin.tv_sec)*1000000 +
-        (tv_end.tv_nsec - tv_begin.tv_nsec)/1000;
-    if (usec > 0)
-    {
-        stat.usec += usec;
-        stat.count++;
-    }
-}
-
-void kv_test_t::print_stats(kv_test_stat_t & prev_stat, timespec & prev_stat_time)
-{
-    timespec cur_stat_time;
-    clock_gettime(CLOCK_REALTIME, &cur_stat_time);
-    int64_t usec = (cur_stat_time.tv_sec - prev_stat_time.tv_sec)*1000000 +
-        (cur_stat_time.tv_nsec - prev_stat_time.tv_nsec)/1000;
-    if (usec > 0)
-    {
-        kv_test_lat_t *lats[] = { &stat.get, &stat.add, &stat.update, &stat.del, &stat.list };
-        kv_test_lat_t *prev[] = { &prev_stat.get, &prev_stat.add, &prev_stat.update, &prev_stat.del, &prev_stat.list };
-        if (!json_output)
-        {
-            char buf[128] = { 0 };
-            for (int i = 0; i < sizeof(lats)/sizeof(lats[0]); i++)
-            {
-                snprintf(buf, sizeof(buf)-1, "%.1f %s/s (%lu us)", (lats[i]->count-prev[i]->count)*1000000.0/usec,
-                    lats[i]->name, (lats[i]->usec-prev[i]->usec)/(lats[i]->count-prev[i]->count > 0 ? lats[i]->count-prev[i]->count : 1));
-                int k;
-                for (k = strlen(buf); k < strlen(lats[i]->name)+21; k++)
-                    buf[k] = ' ';
-                buf[k] = 0;
-                printf("%s", buf);
-            }
-            printf("\n");
-        }
-        else
-        {
-            int64_t runtime = (cur_stat_time.tv_sec - start_stat_time.tv_sec)*1000000 +
-                (cur_stat_time.tv_nsec - start_stat_time.tv_nsec)/1000;
-            printf("{\"runtime\":%.1f", (double)runtime/1000000.0);
-            for (int i = 0; i < sizeof(lats)/sizeof(lats[0]); i++)
-            {
-                if (lats[i]->count > prev[i]->count)
-                {
-                    printf(
-                        ",\"%s\":{\"avg\":{\"iops\":%.1f,\"usec\":%lu},\"total\":{\"count\":%lu,\"usec\":%lu}}",
-                        lats[i]->name, (lats[i]->count-prev[i]->count)*1000000.0/usec,
-                        (lats[i]->usec-prev[i]->usec)/(lats[i]->count-prev[i]->count),
-                        lats[i]->count, lats[i]->usec
-                    );
-                }
-            }
-            printf("}\n");
-        }
-    }
-    prev_stat = stat;
-    prev_stat_time = cur_stat_time;
-}
-
-void kv_test_t::print_total_stats()
-{
-    if (!json_output)
-        printf("Total:\n");
-    kv_test_stat_t start_stats;
-    timespec start_stat_time = this->start_stat_time;
-    print_stats(start_stats, start_stat_time);
-}
-
-void kv_test_t::start_change(const std::string & key)
-{
-    changing_keys.insert(key);
-    for (auto lst: listings)
-    {
-        lst->inflights.insert(key);
-    }
-}
-
-void kv_test_t::stop_change(const std::string & key)
-{
-    changing_keys.erase(key);
-}
-
-int main(int narg, const char *args[])
-{
-    setvbuf(stdout, NULL, _IONBF, 0);
-    setvbuf(stderr, NULL, _IONBF, 0);
-    exe_name = args[0];
-    kv_test_t *p = new kv_test_t();
-    p->run(kv_test_t::parse_args(narg, args));
-    delete p;
-    return 0;
-}
--- a/src/messenger.cpp
+++ b/src/messenger.cpp
@@ -22,7 +22,7 @@ void osd_messenger_t::init()
    {
        rdma_context = msgr_rdma_context_t::create(
            rdma_device != "" ? rdma_device.c_str() : NULL,
-            rdma_port_num, rdma_gid_index, rdma_mtu, rdma_odp, log_level
+            rdma_port_num, rdma_gid_index, rdma_mtu, log_level
        );
        if (!rdma_context)
        {
@@ -42,6 +42,12 @@ void osd_messenger_t::init()
            handle_rdma_events();
        }
    }
+#endif
+#ifndef SO_ZEROCOPY
+    if (log_level > 0)
+    {
+        fprintf(stderr, "Zero-copy TCP send is not supported in this build, ignoring\n");
+    }
 #endif
    keepalive_timer_id = tfd->set_timer(1000, true, [this](int)
    {
@@ -167,13 +173,14 @@ void osd_messenger_t::parse_config(const json11::Json & config)
    this->rdma_max_msg = config["rdma_max_msg"].uint64_value();
    if (!this->rdma_max_msg || this->rdma_max_msg > 128*1024*1024)
        this->rdma_max_msg = 129*1024;
-    this->rdma_odp = config["rdma_odp"].bool_value();
 #endif
    this->receive_buffer_size = (uint32_t)config["tcp_header_buffer_size"].uint64_value();
    if (!this->receive_buffer_size || this->receive_buffer_size > 1024*1024*1024)
        this->receive_buffer_size = 65536;
    this->use_sync_send_recv = config["use_sync_send_recv"].bool_value() ||
        config["use_sync_send_recv"].uint64_value();
+    this->use_zerocopy_send = config["use_zerocopy_send"].bool_value() ||
+        config["use_zerocopy_send"].uint64_value();
    this->peer_connect_interval = config["peer_connect_interval"].uint64_value();
    if (!this->peer_connect_interval)
        this->peer_connect_interval = 5;
@@ -304,8 +311,7 @@ void osd_messenger_t::handle_connect_epoll(int peer_fd)
        on_connect_peer(peer_osd, -result);
        return;
    }
-    int one = 1;
-    setsockopt(peer_fd, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
+    set_socket_options(cl);
    cl->peer_state = PEER_CONNECTED;
    tfd->set_fd_handler(peer_fd, false, [this](int peer_fd, int epoll_events)
    {
@@ -315,6 +321,23 @@ void osd_messenger_t::handle_connect_epoll(int peer_fd)
    check_peer_config(cl);
 }

+void osd_messenger_t::set_socket_options(osd_client_t *cl)
+{
+    int one = 1;
+    setsockopt(cl->peer_fd, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
+#ifdef SO_ZEROCOPY
+    if (!use_zerocopy_send)
+        cl->zerocopy_send = false;
+    else if (setsockopt(cl->peer_fd, SOL_SOCKET, SO_ZEROCOPY, &one, sizeof(one)) != 0)
+    {
+        if (log_level > 0)
+            fprintf(stderr, "[OSD %lu] Failed to enable zero-copy send for client %d: %s\n", this->osd_num, cl->peer_fd, strerror(errno));
+    }
+    else
+        cl->zerocopy_send = true;
+#endif
+}
+
 void osd_messenger_t::handle_peer_epoll(int peer_fd, int epoll_events)
 {
    // Mark client as ready (i.e. some data is available)
@@ -491,14 +514,7 @@ void osd_messenger_t::check_peer_config(osd_client_t *cl)
                    fprintf(stderr, "Connected to OSD %lu using RDMA\n", cl->osd_num);
                }
                cl->peer_state = PEER_RDMA;
-                tfd->set_fd_handler(cl->peer_fd, false, [this](int peer_fd, int epoll_events)
-                {
-                    // Do not miss the disconnection!
-                    if (epoll_events & EPOLLRDHUP)
-                    {
-                        handle_peer_epoll(peer_fd, epoll_events);
-                    }
-                });
+                tfd->set_fd_handler(cl->peer_fd, false, NULL);
                // Add the initial receive request
                try_recv_rdma(cl);
            }
@@ -523,14 +539,13 @@ void osd_messenger_t::accept_connections(int listen_fd)
        fprintf(stderr, "[OSD %lu] new client %d: connection from %s\n", this->osd_num, peer_fd,
            addr_to_string(addr).c_str());
        fcntl(peer_fd, F_SETFL, fcntl(peer_fd, F_GETFL, 0) | O_NONBLOCK);
-        int one = 1;
-        setsockopt(peer_fd, SOL_TCP, TCP_NODELAY, &one, sizeof(one));
-        clients[peer_fd] = new osd_client_t();
-        clients[peer_fd]->peer_addr = addr;
-        clients[peer_fd]->peer_port = ntohs(((sockaddr_in*)&addr)->sin_port);
-        clients[peer_fd]->peer_fd = peer_fd;
-        clients[peer_fd]->peer_state = PEER_CONNECTED;
-        clients[peer_fd]->in_buf = malloc_or_die(receive_buffer_size);
+        auto cl = clients[peer_fd] = new osd_client_t();
+        cl->peer_addr = addr;
+        cl->peer_port = ntohs(((sockaddr_in*)&addr)->sin_port);
+        cl->peer_fd = peer_fd;
+        cl->peer_state = PEER_CONNECTED;
+        cl->in_buf = malloc_or_die(receive_buffer_size);
+        set_socket_options(cl);
        // Add FD to epoll
        tfd->set_fd_handler(peer_fd, false, [this](int peer_fd, int epoll_events)
        {
--- a/src/messenger.h
+++ b/src/messenger.h
@@ -45,6 +45,12 @@ struct msgr_rdma_connection_t;
 struct msgr_rdma_context_t;
 #endif

+struct msgr_zc_not_t
+{
+    osd_op_t *op;
+    uint32_t nsend;
+};
+
 struct osd_client_t
 {
    int refs = 0;
@@ -57,6 +63,7 @@ struct osd_client_t
    int ping_time_remaining = 0;
    int idle_time_remaining = 0;
    osd_num_t osd_num = 0;
+    bool zerocopy_send = false;

    void *in_buf = NULL;

@@ -87,6 +94,12 @@ struct osd_client_t
    int write_state = 0;
    std::vector<iovec> send_list, next_send_list;
    std::vector<msgr_sendp_t> outbox, next_outbox;
+    std::vector<msgr_zc_not_t> zerocopy_sent;
+    uint64_t outbox_size = 0, next_outbox_size = 0;
+    uint32_t zerocopy_notification_idx = 0;
+    uint32_t zerocopy_notification_prev = 0;
+    uint8_t zerocopy_notification_buf[256];
+    struct msghdr zerocopy_notification_msg;

    ~osd_client_t();
 };
@@ -123,6 +136,7 @@ protected:
    int osd_ping_timeout = 0;
    int log_level = 0;
    bool use_sync_send_recv = false;
+    bool use_zerocopy_send = false;

 #ifdef WITH_RDMA
    bool use_rdma = true;
@@ -131,7 +145,6 @@ protected:
    msgr_rdma_context_t *rdma_context = NULL;
    uint64_t rdma_max_sge = 0, rdma_max_send = 0, rdma_max_recv = 0;
    uint64_t rdma_max_msg = 0;
-    bool rdma_odp = false;
 #endif

    std::vector<int> read_ready_clients;
@@ -186,9 +199,11 @@ protected:
    void check_peer_config(osd_client_t *cl);
    void cancel_osd_ops(osd_client_t *cl);
    void cancel_op(osd_op_t *op);
+    void set_socket_options(osd_client_t *cl);

    bool try_send(osd_client_t *cl);
    void handle_send(int result, osd_client_t *cl);
+    void handle_zerocopy_notification(osd_client_t *cl, int res);

    bool handle_read(int result, osd_client_t *cl);
    bool handle_read_buffer(osd_client_t *cl, void *curbuf, int remain);
@@ -198,9 +213,7 @@ protected:
    void handle_reply_ready(osd_op_t *op);

 #ifdef WITH_RDMA
-    void try_send_rdma(osd_client_t *cl);
-    void try_send_rdma_odp(osd_client_t *cl);
-    void try_send_rdma_nodp(osd_client_t *cl);
+    bool try_send_rdma(osd_client_t *cl);
    bool try_recv_rdma(osd_client_t *cl);
    void handle_rdma_events();
 #endif
--- a/src/msgr_rdma.cpp
+++ b/src/msgr_rdma.cpp
@@ -47,29 +47,11 @@ msgr_rdma_connection_t::~msgr_rdma_connection_t()
    if (qp)
        ibv_destroy_qp(qp);
    if (recv_buffers.size())
-    {
        for (auto b: recv_buffers)
-        {
-            if (b.mr)
-                ibv_dereg_mr(b.mr);
-            free(b.buf);
-        }
-        recv_buffers.clear();
-    }
-    if (send_out.mr)
-    {
-        ibv_dereg_mr(send_out.mr);
-        send_out.mr = NULL;
-    }
-    if (send_out.buf)
-    {
-        free(send_out.buf);
-        send_out.buf = NULL;
-    }
-    send_out_size = 0;
+            free(b);
 }

-msgr_rdma_context_t *msgr_rdma_context_t::create(const char *ib_devname, uint8_t ib_port, uint8_t gid_index, uint32_t mtu, bool odp, int log_level)
+msgr_rdma_context_t *msgr_rdma_context_t::create(const char *ib_devname, uint8_t ib_port, uint8_t gid_index, uint32_t mtu, int log_level)
 {
    int res;
    ibv_device **dev_list = NULL;
@@ -154,27 +136,21 @@ msgr_rdma_context_t *msgr_rdma_context_t::create(const char *ib_devname, uint8_t
            fprintf(stderr, "Couldn't query RDMA device for its features\n");
            goto cleanup;
        }
-        ctx->odp = odp;
-        if (ctx->odp &&
-            (!(ctx->attrx.odp_caps.general_caps & IBV_ODP_SUPPORT) ||
+        if (!(ctx->attrx.odp_caps.general_caps & IBV_ODP_SUPPORT) ||
            !(ctx->attrx.odp_caps.general_caps & IBV_ODP_SUPPORT_IMPLICIT) ||
            !(ctx->attrx.odp_caps.per_transport_caps.rc_odp_caps & IBV_ODP_SUPPORT_SEND) ||
-            !(ctx->attrx.odp_caps.per_transport_caps.rc_odp_caps & IBV_ODP_SUPPORT_RECV)))
+            !(ctx->attrx.odp_caps.per_transport_caps.rc_odp_caps & IBV_ODP_SUPPORT_RECV))
        {
-            ctx->odp = false;
-            if (log_level > 0)
-                fprintf(stderr, "The RDMA device isn't implicit ODP (On-Demand Paging) capable, disabling it\n");
+            fprintf(stderr, "The RDMA device isn't implicit ODP (On-Demand Paging) capable or does not support RC send and receive with ODP\n");
+            goto cleanup;
        }
    }

-    if (ctx->odp)
+    ctx->mr = ibv_reg_mr(ctx->pd, NULL, SIZE_MAX, IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_ON_DEMAND);
+    if (!ctx->mr)
    {
-        ctx->mr = ibv_reg_mr(ctx->pd, NULL, SIZE_MAX, IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_ON_DEMAND);
-        if (!ctx->mr)
-        {
-            fprintf(stderr, "Couldn't register RDMA memory region\n");
-            goto cleanup;
-        }
+        fprintf(stderr, "Couldn't register RDMA memory region\n");
+        goto cleanup;
    }

    ctx->channel = ibv_create_comp_channel(ctx->context);
@@ -389,34 +365,12 @@ static void try_send_rdma_wr(osd_client_t *cl, ibv_sge *sge, int op_sge)
    cl->rdma_conn->cur_send++;
 }

-static int try_send_rdma_copy(osd_client_t *cl, uint8_t *dst, int dst_len)
-{
-    auto rc = cl->rdma_conn;
-    int total_dst_len = dst_len;
-    while (dst_len > 0 && rc->send_pos < cl->send_list.size())
-    {
-        iovec & iov = cl->send_list[rc->send_pos];
-        uint32_t len = (uint32_t)(iov.iov_len-rc->send_buf_pos < dst_len
-            ? iov.iov_len-rc->send_buf_pos : dst_len);
-        memcpy(dst, iov.iov_base+rc->send_buf_pos, len);
-        dst += len;
-        dst_len -= len;
-        rc->send_buf_pos += len;
-        if (rc->send_buf_pos >= iov.iov_len)
-        {
-            rc->send_pos++;
-            rc->send_buf_pos = 0;
-        }
-    }
-    return total_dst_len-dst_len;
-}
-
-void osd_messenger_t::try_send_rdma_odp(osd_client_t *cl)
+bool osd_messenger_t::try_send_rdma(osd_client_t *cl)
 {
    auto rc = cl->rdma_conn;
    if (!cl->send_list.size() || rc->cur_send >= rc->max_send)
    {
-        return;
+        return true;
    }
    uint64_t op_size = 0, op_sge = 0;
    ibv_sge sge[rc->max_sge];
@@ -454,70 +408,15 @@ void osd_messenger_t::try_send_rdma_odp(osd_client_t *cl)
        rc->send_sizes.push_back(op_size);
        try_send_rdma_wr(cl, sge, op_sge);
    }
+    return true;
 }

-void osd_messenger_t::try_send_rdma_nodp(osd_client_t *cl)
-{
-    auto rc = cl->rdma_conn;
-    if (!rc->send_out_size)
-    {
-        // Allocate send ring buffer, if not yet
-        rc->send_out_size = rc->max_msg*rdma_max_send;
-        rc->send_out.buf = malloc_or_die(rc->send_out_size);
-        if (!rdma_context->odp)
-        {
-            rc->send_out.mr = ibv_reg_mr(rdma_context->pd, rc->send_out.buf, rc->send_out_size, 0);
-            if (!rc->send_out.mr)
-            {
-                fprintf(stderr, "Failed to register RDMA memory region: %s\n", strerror(errno));
-                exit(1);
-            }
-        }
-    }
-    // Copy data into the buffer and send it
-    uint8_t *dst = NULL;
-    int dst_len = 0;
-    int copied = 1;
-    while (!rc->send_out_full && copied > 0 && rc->cur_send < rc->max_send)
-    {
-        dst = (uint8_t*)rc->send_out.buf + rc->send_out_pos;
-        dst_len = (rc->send_out_pos < rc->send_out_size ? rc->send_out_size-rc->send_out_pos : rc->send_done_pos-rc->send_out_pos);
-        if (dst_len > rc->max_msg)
-            dst_len = rc->max_msg;
-        copied = try_send_rdma_copy(cl, dst, dst_len);
-        if (copied > 0)
-        {
-            rc->send_out_pos += copied;
-            if (rc->send_out_pos == rc->send_out_size)
-                rc->send_out_pos = 0;
-            assert(rc->send_out_pos < rc->send_out_size);
-            if (rc->send_out_pos >= rc->send_done_pos)
-                rc->send_out_full = true;
-            ibv_sge sge = {
-                .addr = (uintptr_t)dst,
-                .length = (uint32_t)copied,
-                .lkey = rdma_context->odp ? rdma_context->mr->lkey : rc->send_out.mr->lkey,
-            };
-            try_send_rdma_wr(cl, &sge, 1);
-            rc->send_sizes.push_back(copied);
-        }
-    }
-}
-
-void osd_messenger_t::try_send_rdma(osd_client_t *cl)
-{
-    if (rdma_context->odp)
-        try_send_rdma_odp(cl);
-    else
-        try_send_rdma_nodp(cl);
-}
-
-static void try_recv_rdma_wr(osd_client_t *cl, msgr_rdma_buf_t b)
+static void try_recv_rdma_wr(osd_client_t *cl, void *buf)
 {
    ibv_sge sge = {
-        .addr = (uintptr_t)b.buf,
+        .addr = (uintptr_t)buf,
        .length = (uint32_t)cl->rdma_conn->max_msg,
-        .lkey = cl->rdma_conn->ctx->odp ? cl->rdma_conn->ctx->mr->lkey : b.mr->lkey,
+        .lkey = cl->rdma_conn->ctx->mr->lkey,
    };
    ibv_recv_wr *bad_wr = NULL;
    ibv_recv_wr wr = {
@@ -539,19 +438,9 @@ bool osd_messenger_t::try_recv_rdma(osd_client_t *cl)
    auto rc = cl->rdma_conn;
    while (rc->cur_recv < rc->max_recv)
    {
-        msgr_rdma_buf_t b;
-        b.buf = malloc_or_die(rc->max_msg);
-        if (!rdma_context->odp)
-        {
-            b.mr = ibv_reg_mr(rdma_context->pd, b.buf, rc->max_msg, IBV_ACCESS_LOCAL_WRITE);
-            if (!b.mr)
-            {
-                fprintf(stderr, "Failed to register RDMA memory region: %s\n", strerror(errno));
-                exit(1);
-            }
-        }
-        rc->recv_buffers.push_back(b);
-        try_recv_rdma_wr(cl, b);
+        void *buf = malloc_or_die(rc->max_msg);
+        rc->recv_buffers.push_back(buf);
+        try_recv_rdma_wr(cl, buf);
    }
    return true;
 }
@@ -603,7 +492,7 @@ void osd_messenger_t::handle_rdma_events()
            if (!is_send)
            {
                rc->cur_recv--;
-                if (!handle_read_buffer(cl, rc->recv_buffers[rc->next_recv_buf].buf, wc[i].byte_len))
+                if (!handle_read_buffer(cl, rc->recv_buffers[rc->next_recv_buf], wc[i].byte_len))
                {
                    // handle_read_buffer may stop the client
                    continue;
@@ -616,14 +505,6 @@ void osd_messenger_t::handle_rdma_events()
                rc->cur_send--;
                uint64_t sent_size = rc->send_sizes.at(0);
                rc->send_sizes.erase(rc->send_sizes.begin(), rc->send_sizes.begin()+1);
-                if (!rdma_context->odp)
-                {
-                    rc->send_done_pos += sent_size;
-                    rc->send_out_full = false;
-                    if (rc->send_done_pos == rc->send_out_size)
-                        rc->send_done_pos = 0;
-                    assert(rc->send_done_pos < rc->send_out_size);
-                }
                int send_pos = 0, send_buf_pos = 0;
                while (sent_size > 0)
                {
--- a/src/msgr_rdma.h
+++ b/src/msgr_rdma.h
@@ -23,7 +23,6 @@ struct msgr_rdma_context_t
    ibv_device *dev = NULL;
    ibv_device_attr_ex attrx;
    ibv_pd *pd = NULL;
-    bool odp = false;
    ibv_mr *mr = NULL;
    ibv_comp_channel *channel = NULL;
    ibv_cq *cq = NULL;
@@ -36,16 +35,10 @@ struct msgr_rdma_context_t
    int max_cqe = 0;
    int used_max_cqe = 0;

-    static msgr_rdma_context_t *create(const char *ib_devname, uint8_t ib_port, uint8_t gid_index, uint32_t mtu, bool odp, int log_level);
+    static msgr_rdma_context_t *create(const char *ib_devname, uint8_t ib_port, uint8_t gid_index, uint32_t mtu, int log_level);
    ~msgr_rdma_context_t();
 };

-struct msgr_rdma_buf_t
-{
-    void *buf = NULL;
-    ibv_mr *mr = NULL;
-};
-
 struct msgr_rdma_connection_t
 {
    msgr_rdma_context_t *ctx = NULL;
@@ -57,11 +50,8 @@ struct msgr_rdma_connection_t

    int send_pos = 0, send_buf_pos = 0;
    int next_recv_buf = 0;
-    std::vector<msgr_rdma_buf_t> recv_buffers;
+    std::vector<void*> recv_buffers;
    std::vector<uint64_t> send_sizes;
-    msgr_rdma_buf_t send_out;
-    int send_out_pos = 0, send_done_pos = 0, send_out_size = 0;
-    bool send_out_full = false;

    ~msgr_rdma_connection_t();
    static msgr_rdma_connection_t *create(msgr_rdma_context_t *ctx, uint32_t max_send, uint32_t max_recv, uint32_t max_sge, uint32_t max_msg);
--- a/src/msgr_send.cpp
+++ b/src/msgr_send.cpp
@@ -3,10 +3,15 @@

 #define _XOPEN_SOURCE
 #include <limits.h>
-#include <sys/epoll.h>

 #include "messenger.h"

+#include <linux/errqueue.h>
+
+#ifndef MSG_ZEROCOPY
+#define MSG_ZEROCOPY 0
+#endif
+
 void osd_messenger_t::outbox_push(osd_op_t *cur_op)
 {
    assert(cur_op->peer_fd);
@@ -37,6 +42,7 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
    }
    auto & to_send_list = cl->write_msg.msg_iovlen ? cl->next_send_list : cl->send_list;
    auto & to_outbox = cl->write_msg.msg_iovlen ? cl->next_outbox : cl->outbox;
+    auto & to_size = cl->write_msg.msg_iovlen ? cl->next_outbox_size : cl->outbox_size;
    if (cur_op->op_type == OSD_OP_IN)
    {
        measure_exec(cur_op);
@@ -47,6 +53,7 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
        to_send_list.push_back((iovec){ .iov_base = cur_op->req.buf, .iov_len = OSD_PACKET_SIZE });
        cl->sent_ops[cur_op->req.hdr.id] = cur_op;
    }
+    to_size += OSD_PACKET_SIZE;
    to_outbox.push_back((msgr_sendp_t){ .op = cur_op, .flags = MSGR_SENDP_HDR });
    // Bitmap
    if (cur_op->op_type == OSD_OP_IN &&
@@ -58,6 +65,7 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
            .iov_len = cur_op->reply.sec_rw.attr_len,
        });
        to_outbox.push_back((msgr_sendp_t){ .op = cur_op, .flags = 0 });
+        to_size += cur_op->reply.sec_rw.attr_len;
    }
    else if (cur_op->op_type == OSD_OP_OUT &&
        (cur_op->req.hdr.opcode == OSD_OP_SEC_WRITE || cur_op->req.hdr.opcode == OSD_OP_SEC_WRITE_STABLE) &&
@@ -68,6 +76,7 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
            .iov_len = cur_op->req.sec_rw.attr_len,
        });
        to_outbox.push_back((msgr_sendp_t){ .op = cur_op, .flags = 0 });
+        to_size += cur_op->req.sec_rw.attr_len;
    }
    // Operation data
    if ((cur_op->op_type == OSD_OP_IN
@@ -90,15 +99,22 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
                assert(cur_op->iov.buf[i].iov_base);
                to_send_list.push_back(cur_op->iov.buf[i]);
                to_outbox.push_back((msgr_sendp_t){ .op = cur_op, .flags = 0 });
+                to_size += cur_op->iov.buf[i].iov_len;
            }
        }
    }
    if (cur_op->req.hdr.opcode == OSD_OP_SEC_READ_BMP)
    {
        if (cur_op->op_type == OSD_OP_IN && cur_op->reply.hdr.retval > 0)
+        {
            to_send_list.push_back((iovec){ .iov_base = cur_op->buf, .iov_len = (size_t)cur_op->reply.hdr.retval });
+            to_size += cur_op->reply.hdr.retval;
+        }
        else if (cur_op->op_type == OSD_OP_OUT && cur_op->req.sec_read_bmp.len > 0)
+        {
            to_send_list.push_back((iovec){ .iov_base = cur_op->buf, .iov_len = (size_t)cur_op->req.sec_read_bmp.len });
+            to_size += cur_op->req.sec_read_bmp.len;
+        }
        to_outbox.push_back((msgr_sendp_t){ .op = cur_op, .flags = 0 });
    }
    if (cur_op->op_type == OSD_OP_IN)
@@ -184,17 +200,19 @@ bool osd_messenger_t::try_send(osd_client_t *cl)
        }
        cl->write_msg.msg_iov = cl->send_list.data();
        cl->write_msg.msg_iovlen = cl->send_list.size() < IOV_MAX ? cl->send_list.size() : IOV_MAX;
+        cl->write_msg.msg_flags = (cl->zerocopy_send && (cl->outbox_size/cl->send_list.size()) >= 4096 ? MSG_ZEROCOPY : 0);
        cl->refs++;
        ring_data_t* data = ((ring_data_t*)sqe->user_data);
        data->callback = [this, cl](ring_data_t *data) { handle_send(data->res, cl); };
-        my_uring_prep_sendmsg(sqe, peer_fd, &cl->write_msg, 0);
+        my_uring_prep_sendmsg(sqe, peer_fd, &cl->write_msg, cl->write_msg.msg_flags);
    }
    else
    {
        cl->write_msg.msg_iov = cl->send_list.data();
        cl->write_msg.msg_iovlen = cl->send_list.size() < IOV_MAX ? cl->send_list.size() : IOV_MAX;
+        cl->write_msg.msg_flags = (cl->zerocopy_send && (cl->outbox_size/cl->send_list.size()) >= 4096 ? MSG_ZEROCOPY : 0);
        cl->refs++;
-        int result = sendmsg(peer_fd, &cl->write_msg, MSG_NOSIGNAL);
+        int result = sendmsg(peer_fd, &cl->write_msg, MSG_NOSIGNAL | cl->write_msg.msg_flags);
        if (result < 0)
        {
            result = -errno;
@@ -204,6 +222,62 @@ bool osd_messenger_t::try_send(osd_client_t *cl)
    return true;
 }

+void osd_messenger_t::handle_zerocopy_notification(osd_client_t *cl, int res)
+{
+    cl->refs--;
+    if (cl->peer_state == PEER_STOPPED)
+    {
+        if (cl->refs <= 0)
+        {
+            delete cl;
+        }
+        return;
+    }
+    if (res != 0)
+    {
+        return;
+    }
+    if (cl->zerocopy_notification_msg.msg_flags & MSG_CTRUNC)
+    {
+        fprintf(stderr, "zero-copy send notification truncated on client socket %d\n", cl->peer_fd);
+        return;
+    }
+    for (struct cmsghdr *cm = CMSG_FIRSTHDR(&cl->zerocopy_notification_msg); cm; cm = CMSG_NXTHDR(&cl->zerocopy_notification_msg, cm))
+    {
+        if (cm->cmsg_level == SOL_IP && cm->cmsg_type == IP_RECVERR)
+        {
+            struct sock_extended_err *serr = (struct sock_extended_err*)CMSG_DATA(cm);
+            if (serr->ee_errno == 0 && serr->ee_origin == SO_EE_ORIGIN_ZEROCOPY)
+            {
+                // completed sends numbered serr->ee_info .. serr->ee_data
+                int start = 0;
+                while (start < cl->zerocopy_sent.size() && cl->zerocopy_sent[start].nsend < serr->ee_info)
+                    start++;
+                int end = start;
+                if (serr->ee_data < serr->ee_info)
+                {
+                    // counter has wrapped around
+                    while (end < cl->zerocopy_sent.size() && cl->zerocopy_sent[end].nsend >= cl->zerocopy_sent[start].nsend)
+                        end++;
+                }
+                while (end < cl->zerocopy_sent.size() && cl->zerocopy_sent[end].nsend <= serr->ee_data)
+                    end++;
+                if (end > start)
+                {
+                    for (int i = start; i < end; i++)
+                    {
+                        delete cl->zerocopy_sent[i].op;
+                    }
+                    cl->zerocopy_sent.erase(
+                        cl->zerocopy_sent.begin() + start,
+                        cl->zerocopy_sent.begin() + end
+                    );
+                }
+            }
+        }
+    }
+}
+
 void osd_messenger_t::send_replies()
 {
    for (int i = 0; i < write_ready_clients.size(); i++)
@@ -231,16 +305,19 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
        }
        return;
    }
-    if (result < 0 && result != -EAGAIN && result != -EINTR)
+    if (result < 0 && result != -EAGAIN && result != -EINTR && result != -ENOBUFS)
    {
        // this is a client socket, so don't panic. just disconnect it
        fprintf(stderr, "Client %d socket write error: %d (%s). Disconnecting client\n", cl->peer_fd, -result, strerror(-result));
        stop_client(cl->peer_fd);
        return;
    }
+    bool used_zerocopy = false;
    if (result >= 0)
    {
+        used_zerocopy = (cl->write_msg.msg_flags & MSG_ZEROCOPY) ? true : false;
        int done = 0;
+        int bytes_written = result;
        while (result > 0 && done < cl->send_list.size())
        {
            iovec & iov = cl->send_list[done];
@@ -249,7 +326,19 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
                if (cl->outbox[done].flags & MSGR_SENDP_FREE)
                {
                    // Reply fully sent
-                    delete cl->outbox[done].op;
+                    if (!used_zerocopy)
+                    {
+                        delete cl->outbox[done].op;
+                    }
+                    else
+                    {
+                        // With zero-copy send the difference is that we must keep the buffer (i.e. the operation)
+                        // allocated until we get send notification from MSG_ERRQUEUE
+                        cl->zerocopy_sent.push_back((msgr_zc_not_t){
+                            .op = cl->outbox[done].op,
+                            .nsend = cl->zerocopy_notification_idx,
+                        });
+                    }
                }
                result -= iov.iov_len;
                done++;
@@ -261,6 +350,11 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
                break;
            }
        }
+        if (used_zerocopy)
+        {
+            cl->zerocopy_notification_idx++;
+        }
+        cl->outbox_size -= bytes_written;
        if (done > 0)
        {
            cl->send_list.erase(cl->send_list.begin(), cl->send_list.begin()+done);
@@ -270,8 +364,10 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
        {
            cl->send_list.insert(cl->send_list.end(), cl->next_send_list.begin(), cl->next_send_list.end());
            cl->outbox.insert(cl->outbox.end(), cl->next_outbox.begin(), cl->next_outbox.end());
+            cl->outbox_size += cl->next_outbox_size;
            cl->next_send_list.clear();
            cl->next_outbox.clear();
+            cl->next_outbox_size = 0;
        }
        cl->write_state = cl->outbox.size() > 0 ? CL_WRITE_READY : 0;
 #ifdef WITH_RDMA
@@ -284,14 +380,7 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
                fprintf(stderr, "Successfully connected with client %d using RDMA\n", cl->peer_fd);
            }
            cl->peer_state = PEER_RDMA;
-            tfd->set_fd_handler(cl->peer_fd, false, [this](int peer_fd, int epoll_events)
-            {
-                // Do not miss the disconnection!
-                if (epoll_events & EPOLLRDHUP)
-                {
-                    handle_peer_epoll(peer_fd, epoll_events);
-                }
-            });
+            tfd->set_fd_handler(cl->peer_fd, false, NULL);
            // Add the initial receive request
            try_recv_rdma(cl);
        }
@@ -301,4 +390,34 @@ void osd_messenger_t::handle_send(int result, osd_client_t *cl)
    {
        write_ready_clients.push_back(cl->peer_fd);
    }
+    if (used_zerocopy && (cl->zerocopy_notification_idx-cl->zerocopy_notification_prev) >= 16 &&
+        cl->zerocopy_sent.size() > 0)
+    {
+        cl->zerocopy_notification_prev = cl->zerocopy_notification_idx;
+        cl->zerocopy_notification_msg = {
+            .msg_control = cl->zerocopy_notification_buf,
+            .msg_controllen = sizeof(cl->zerocopy_notification_buf),
+        };
+        cl->refs++;
+        io_uring_sqe* sqe = NULL;
+        if (ringloop && !use_sync_send_recv)
+        {
+            sqe = ringloop->get_sqe();
+        }
+        if (!sqe)
+        {
+            int res = recvmsg(cl->peer_fd, &cl->zerocopy_notification_msg, MSG_ERRQUEUE|MSG_DONTWAIT);
+            if (res < 0)
+            {
+                res = -errno;
+            }
+            handle_zerocopy_notification(cl, res);
+        }
+        else
+        {
+            ring_data_t* data = ((ring_data_t*)sqe->user_data);
+            data->callback = [this, cl](ring_data_t *data) { handle_zerocopy_notification(cl, data->res); };
+            my_uring_prep_recvmsg(sqe, cl->peer_fd, &cl->zerocopy_notification_msg, MSG_ERRQUEUE);
+        }
+    }
 }
--- a/src/nbd_proxy.cpp
+++ b/src/nbd_proxy.cpp
@@ -225,7 +225,7 @@ public:
            cfg = obj;
        }
        // Create client
-        ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+        ringloop = new ring_loop_t(512);
        epmgr = new epoll_manager_t(ringloop);
        cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
        if (!inode)
--- a/src/nfs_proxy.cpp
+++ b/src/nfs_proxy.cpp
@@ -124,7 +124,7 @@ void nfs_proxy_t::run(json11::Json cfg)
        cfg = obj;
    }
    // Create client
-    ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    ringloop = new ring_loop_t(512);
    epmgr = new epoll_manager_t(ringloop);
    cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
    cmd = new cli_tool_t();
--- a/src/osd.cpp
+++ b/src/osd.cpp
@@ -541,15 +541,11 @@ void osd_t::print_slow()
                }
                else if (op->req.hdr.opcode == OSD_OP_SEC_STABILIZE || op->req.hdr.opcode == OSD_OP_SEC_ROLLBACK)
                {
-                    for (uint64_t i = 0; i < op->req.sec_stab.len && i < sizeof(obj_ver_id)*12; i += sizeof(obj_ver_id))
+                    for (uint64_t i = 0; i < op->req.sec_stab.len; i += sizeof(obj_ver_id))
                    {
                        obj_ver_id *ov = (obj_ver_id*)((uint8_t*)op->buf + i);
                        bufprintf(i == 0 ? " %lx:%lx v%lu" : ", %lx:%lx v%lu", ov->oid.inode, ov->oid.stripe, ov->version);
                    }
-                    if (op->req.sec_stab.len > sizeof(obj_ver_id)*12)
-                    {
-                        bufprintf(", ... (%lu items)", op->req.sec_stab.len/sizeof(obj_ver_id));
-                    }
                }
                else if (op->req.hdr.opcode == OSD_OP_SEC_LIST)
                {
--- a/src/osd_main.cpp
+++ b/src/osd_main.cpp
@@ -19,14 +19,6 @@ static void handle_sigint(int sig)
    exit(0);
 }

-static const char* help_text =
-    "Vitastor OSD (block object storage daemon) " VERSION "\n"
-    "(c) Vitaliy Filippov, 2019+ (VNPL-1.1)\n"
-    "\n"
-    "OSDs are usually started by vitastor-disk.\n"
-    "Manual usage: vitastor-osd [--option value] ...\n"
-;
-
 int main(int narg, char *args[])
 {
    setvbuf(stdout, NULL, _IONBF, 0);
@@ -45,20 +37,10 @@ int main(int narg, char *args[])
            char *opt = args[i]+2;
            config[std::string(opt)] = std::string(args[++i]);
        }
-        else if (!strcmp(args[i], "--help"))
-        {
-            printf("%s", help_text);
-            return 0;
-        }
-    }
-    if (!config.size())
-    {
-        printf("%s", help_text);
-        return 1;
    }
    signal(SIGINT, handle_sigint);
    signal(SIGTERM, handle_sigint);
-    ring_loop_t *ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    ring_loop_t *ringloop = new ring_loop_t(512);
    osd = new osd_t(config, ringloop);
    while (1)
    {
--- a/src/ringloop.cpp
+++ b/src/ringloop.cpp
@@ -17,7 +17,7 @@ ring_loop_t::ring_loop_t(int qd)
    {
        throw std::runtime_error(std::string("io_uring_queue_init: ") + strerror(-ret));
    }
-    free_ring_data_ptr = *ring.sq.kring_entries;
+    free_ring_data_ptr = *ring.cq.kring_entries;
    ring_datas = (struct ring_data_t*)calloc(free_ring_data_ptr, sizeof(ring_data_t));
    free_ring_data = (int*)malloc(sizeof(int) * free_ring_data_ptr);
    if (!ring_datas || !free_ring_data)
--- a/src/ringloop.h
+++ b/src/ringloop.h
@@ -15,8 +15,6 @@
 #include <functional>
 #include <vector>

-#define RINGLOOP_DEFAULT_SIZE 1024
-
 static inline void my_uring_prep_rw(int op, struct io_uring_sqe *sqe, int fd, const void *addr, unsigned len, off_t offset)
 {
    // Prepare a read/write operation without clearing user_data
@@ -141,9 +139,11 @@ public:
        if (free_ring_data_ptr == 0)
            return NULL;
        struct io_uring_sqe* sqe = io_uring_get_sqe(&ring);
-        assert(sqe);
-        *sqe = { 0 };
-        io_uring_sqe_set_data(sqe, ring_datas + free_ring_data[--free_ring_data_ptr]);
+        if (sqe)
+        {
+            *sqe = { 0 };
+            io_uring_sqe_set_data(sqe, ring_datas + free_ring_data[--free_ring_data_ptr]);
+        }
        return sqe;
    }
    inline void set_immediate(const std::function<void()> cb)
--- a/src/stub_uring_osd.cpp
+++ b/src/stub_uring_osd.cpp
@@ -30,7 +30,7 @@ void stub_exec_op(osd_messenger_t *msgr, osd_op_t *op);
 int main(int narg, char *args[])
 {
    ring_consumer_t looper;
-    ring_loop_t *ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    ring_loop_t *ringloop = new ring_loop_t(512);
    epoll_manager_t *epmgr = new epoll_manager_t(ringloop);
    osd_messenger_t *msgr = new osd_messenger_t();
    msgr->osd_num = 1351;
--- a/src/test_blockstore.cpp
+++ b/src/test_blockstore.cpp
@@ -11,7 +11,7 @@ int main(int narg, char *args[])
    config["meta_device"] = "./test_meta.bin";
    config["journal_device"] = "./test_journal.bin";
    config["data_device"] = "./test_data.bin";
-    ring_loop_t *ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    ring_loop_t *ringloop = new ring_loop_t(512);
    epoll_manager_t *epmgr = new epoll_manager_t(ringloop);
    blockstore_t *bs = new blockstore_t(config, ringloop, epmgr->tfd);

--- a/src/test_cas.cpp
+++ b/src/test_cas.cpp
@@ -68,7 +68,7 @@ int main(int narg, char *args[])
        | cfg["inode_id"].uint64_value();
    uint64_t base_ver = 0;
    // Create client
-    auto ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+    auto ringloop = new ring_loop_t(512);
    auto epmgr = new epoll_manager_t(ringloop);
    auto cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
    cli->on_ready([&]()
--- a/src/vitastor.pc.in
+++ b/src/vitastor.pc.in
@@ -6,7 +6,7 @@ includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@

 Name: Vitastor
 Description: Vitastor client library
-Version: 1.2.0
+Version: 1.1.0
 Libs: -L${libdir} -lvitastor_client
 Cflags: -I${includedir}

--- a/src/vitastor_c.cpp
+++ b/src/vitastor_c.cpp
@@ -114,7 +114,7 @@ vitastor_c *vitastor_c_create_qemu_uring(QEMUSetFDHandler *aio_set_fd_handler, v
    ring_loop_t *ringloop = NULL;
    try
    {
-        ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+        ringloop = new ring_loop_t(512);
    }
    catch (std::exception & e)
    {
@@ -136,7 +136,7 @@ vitastor_c *vitastor_c_create_uring(const char *config_path, const char *etcd_ho
    ring_loop_t *ringloop = NULL;
    try
    {
-        ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+        ringloop = new ring_loop_t(512);
    }
    catch (std::exception & e)
    {
@@ -167,7 +167,7 @@ vitastor_c *vitastor_c_create_uring_json(const char **options, int options_len)
    ring_loop_t *ringloop = NULL;
    try
    {
-        ringloop = new ring_loop_t(RINGLOOP_DEFAULT_SIZE);
+        ringloop = new ring_loop_t(512);
    }
    catch (std::exception & e)
    {