From de6919b02bb7cb70ccd3842910b4474798b2f76c Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Sat, 12 Sep 2020 19:14:51 +0300
Subject: [PATCH] Add option to disable multiple overwrites of the same journal
 sector

This makes sense for some SSDs like Intel D3-4510 because they don't
like overwrites of the same sector:

$ fio -direct=1 -rw=write -bs=4k -size=4k -loops=100000 -iodepth=1
  write: IOPS=3142, BW=12.3MiB/s (12.9MB/s)(97.9MiB/7977msec)

$ fio -direct=1 -rw=write -bs=4k -size=128k -loops=100000 -iodepth=1
  write: IOPS=20.8k, BW=81.4MiB/s (85.3MB/s)(543MiB/6675msec)
---
 blockstore_journal.cpp | 9 +++++++--
 blockstore_journal.h   | 2 ++
 blockstore_open.cpp    | 2 ++
 lp/mon.js              | 1 +
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/blockstore_journal.cpp b/blockstore_journal.cpp
index 41d1c423..525ea7ba 100644
--- a/blockstore_journal.cpp
+++ b/blockstore_journal.cpp
@@ -17,7 +17,9 @@ int blockstore_journal_check_t::check_available(blockstore_op_t *op, int entries
     int required = entries_required;
     while (1)
     {
-        int fits = (bs->journal.block_size - next_in_pos) / size;
+        int fits = bs->journal.no_same_sector_overwrites && bs->journal.sector_info[next_sector].written
+            ? 0
+            : (bs->journal.block_size - next_in_pos) / size;
         if (fits > 0)
         {
             if (first_sector == -1)
@@ -110,10 +112,12 @@ int blockstore_journal_check_t::check_available(blockstore_op_t *op, int entries
 
 journal_entry* prefill_single_journal_entry(journal_t & journal, uint16_t type, uint32_t size)
 {
-    if (journal.block_size - journal.in_sector_pos < size)
+    if (journal.block_size - journal.in_sector_pos < size ||
+        journal.no_same_sector_overwrites && journal.sector_info[journal.cur_sector].written)
     {
         assert(!journal.sector_info[journal.cur_sector].dirty);
         // Move to the next journal sector
+        journal.sector_info[journal.cur_sector].written = false;
         if (journal.sector_info[journal.cur_sector].usage_count > 0)
         {
             // Also select next sector buffer in memory
@@ -148,6 +152,7 @@ journal_entry* prefill_single_journal_entry(journal_t & journal, uint16_t type,
 void prepare_journal_sector_write(journal_t & journal, int cur_sector, io_uring_sqe *sqe, std::function<void(ring_data_t*)> cb)
 {
     journal.sector_info[cur_sector].dirty = false;
+    journal.sector_info[cur_sector].written = true;
     journal.sector_info[cur_sector].usage_count++;
     ring_data_t *data = ((ring_data_t*)sqe->user_data);
     data->iov = (struct iovec){
diff --git a/blockstore_journal.h b/blockstore_journal.h
index b7ddf430..a0d2e5eb 100644
--- a/blockstore_journal.h
+++ b/blockstore_journal.h
@@ -129,6 +129,7 @@ struct journal_sector_info_t
 {
     uint64_t offset;
     uint64_t usage_count;
+    bool written;
     bool dirty;
 };
 
@@ -153,6 +154,7 @@ struct journal_t
     void *sector_buf = NULL;
     journal_sector_info_t *sector_info = NULL;
     uint64_t sector_count;
+    bool no_same_sector_overwrites = false;
     int cur_sector = 0;
     int in_sector_pos = 0;
 
diff --git a/blockstore_open.cpp b/blockstore_open.cpp
index 487f21d6..76c2d815 100644
--- a/blockstore_open.cpp
+++ b/blockstore_open.cpp
@@ -59,6 +59,8 @@ void blockstore_impl_t::parse_config(blockstore_config_t & config)
     journal_device = config["journal_device"];
     journal.offset = strtoull(config["journal_offset"].c_str(), NULL, 10);
     journal.sector_count = strtoull(config["journal_sector_buffer_count"].c_str(), NULL, 10);
+    journal.no_same_sector_overwrites = config["journal_no_same_sector_overwrites"] == "true" ||
+        config["journal_no_same_sector_overwrites"] == "1" || config["journal_no_same_sector_overwrites"] == "yes";
     journal.inmemory = config["inmemory_journal"] != "false";
     disk_alignment = strtoull(config["disk_alignment"].c_str(), NULL, 10);
     journal_block_size = strtoull(config["journal_block_size"].c_str(), NULL, 10);
diff --git a/lp/mon.js b/lp/mon.js
index 52804c72..2b2a708c 100644
--- a/lp/mon.js
+++ b/lp/mon.js
@@ -81,6 +81,7 @@ class Mon
                 inmemory_metadata,
                 inmemory_journal,
                 journal_sector_buffer_count,
+                journal_no_same_sector_overwrites,
             }, */
             global: {},
             /* node_placement: {