53 lines
1.5 KiB
Diff
53 lines
1.5 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Stefan Reiter <s.reiter@proxmox.com>
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Date: Wed, 9 Dec 2020 11:46:57 +0100
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Subject: [PATCH] PVE: block/pbs: fast-path reads without allocation if
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possible
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...and switch over to g_malloc/g_free while at it to align with other
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QEMU code.
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Tracing shows the fast-path is taken almost all the time, though not
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100% so the slow one is still necessary.
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Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
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---
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block/pbs.c | 17 ++++++++++++++---
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1 file changed, 14 insertions(+), 3 deletions(-)
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diff --git a/block/pbs.c b/block/pbs.c
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index 78dad0dcc4..ac54e816c0 100644
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--- a/block/pbs.c
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+++ b/block/pbs.c
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@@ -200,7 +200,16 @@ static coroutine_fn int pbs_co_preadv(BlockDriverState *bs,
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BDRVPBSState *s = bs->opaque;
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int ret;
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char *pbs_error = NULL;
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- uint8_t *buf = malloc(bytes);
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+ uint8_t *buf;
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+ bool inline_buf = true;
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+
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+ /* for single-buffer IO vectors we can fast-path the write directly to it */
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+ if (qiov->niov == 1 && qiov->iov->iov_len >= bytes) {
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+ buf = qiov->iov->iov_base;
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+ } else {
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+ inline_buf = false;
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+ buf = g_malloc(bytes);
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+ }
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ReadCallbackData rcb = {
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.co = qemu_coroutine_self(),
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@@ -218,8 +227,10 @@ static coroutine_fn int pbs_co_preadv(BlockDriverState *bs,
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return -EIO;
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}
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- qemu_iovec_from_buf(qiov, 0, buf, bytes);
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- free(buf);
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+ if (!inline_buf) {
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+ qemu_iovec_from_buf(qiov, 0, buf, bytes);
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+ g_free(buf);
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+ }
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return ret;
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}
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