From: Wolfgang Bumiller <w.bumiller@proxmox.com>
To: Stefan Reiter <s.reiter@proxmox.com>
Cc: pve-devel@lists.proxmox.com, pbs-devel@lists.proxmox.com
Subject: Re: [pbs-devel] [pve-devel] [PATCH qemu 02/11] PVE: block/pbs: fast-path reads without allocation if possible
Date: Tue, 12 Jan 2021 10:29:20 +0100 [thread overview]
Message-ID: <20210112092920.g4hsrih5pa6uvqbq@wobu-vie.proxmox.com> (raw)
In-Reply-To: <20210111111409.32385-3-s.reiter@proxmox.com>
On Mon, Jan 11, 2021 at 12:14:00PM +0100, Stefan Reiter wrote:
> ...and switch over to g_malloc/g_free while at it to align with other
> QEMU code.
>
> Tracing shows the fast-path is taken almost all the time, though not
> 100% so the slow one is still necessary.
I wonder if vectored reads could be implemented directly at the
library&rust code level... this would probably have to go all the way
from here to the hyper request code though, since it's not really part
of AsyncRead :-\
> Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
> ---
>
> For that slight unnoticable performance boost :)
>
> block/pbs.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/block/pbs.c b/block/pbs.c
> index 1481a2bfd1..fbf0d8d845 100644
> --- a/block/pbs.c
> +++ b/block/pbs.c
> @@ -200,7 +200,16 @@ static coroutine_fn int pbs_co_preadv(BlockDriverState *bs,
> BDRVPBSState *s = bs->opaque;
> int ret;
> char *pbs_error = NULL;
> - uint8_t *buf = malloc(bytes);
> + uint8_t *buf;
> + bool inline_buf = true;
> +
> + /* for single-buffer IO vectors we can fast-path the write directly to it */
> + if (qiov->niov == 1 && qiov->iov->iov_len >= bytes) {
> + buf = qiov->iov->iov_base;
> + } else {
> + inline_buf = false;
> + buf = g_malloc(bytes);
> + }
>
> ReadCallbackData rcb = {
> .co = qemu_coroutine_self(),
> @@ -218,8 +227,10 @@ static coroutine_fn int pbs_co_preadv(BlockDriverState *bs,
> return -EIO;
> }
>
> - qemu_iovec_from_buf(qiov, 0, buf, bytes);
> - free(buf);
> + if (!inline_buf) {
> + qemu_iovec_from_buf(qiov, 0, buf, bytes);
> + g_free(buf);
> + }
>
> return ret;
> }
> --
> 2.20.1
next prev parent reply other threads:[~2021-01-12 9:29 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 11:13 [pbs-devel] [PATCH 00/11] live-restore for PBS snapshots Stefan Reiter
2021-01-11 11:13 ` [pbs-devel] [PATCH qemu 01/11] PVE: explicitly add libuuid as linking dependency Stefan Reiter
2021-01-12 12:04 ` Thomas Lamprecht
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu 02/11] PVE: block/pbs: fast-path reads without allocation if possible Stefan Reiter
2021-01-12 9:29 ` Wolfgang Bumiller [this message]
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu 03/11] block: add alloc-track driver Stefan Reiter
2021-01-12 10:54 ` [pbs-devel] [pve-devel] " Wolfgang Bumiller
2021-01-12 11:29 ` Stefan Reiter
2021-01-12 13:42 ` Wolfgang Bumiller
2021-01-11 11:14 ` [pbs-devel] [PATCH proxmox-backup 04/11] RemoteChunkReader: add LRU cached variant Stefan Reiter
2021-01-11 11:14 ` [pbs-devel] [PATCH proxmox-backup-qemu 05/11] access: use bigger cache and LRU chunk reader Stefan Reiter
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu-server 06/11] make qemu_drive_mirror_monitor more generic Stefan Reiter
2021-01-12 13:19 ` [pbs-devel] [pve-devel] " Wolfgang Bumiller
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu-server 07/11] cfg2cmd: allow PBS snapshots as backing files for drives Stefan Reiter
2021-01-28 16:25 ` [pbs-devel] [pve-devel] " Thomas Lamprecht
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu-server 08/11] enable live-restore for PBS Stefan Reiter
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu-server 09/11] extract register_qmeventd_handle to QemuServer.pm Stefan Reiter
2021-01-11 11:14 ` [pbs-devel] [PATCH qemu-server 10/11] live-restore: register qmeventd handle Stefan Reiter
2021-01-11 11:14 ` [pbs-devel] [PATCH manager 11/11] ui: restore: add live-restore checkbox Stefan Reiter
2021-01-11 15:50 ` [pbs-devel] [pve-devel] [PATCH 00/11] live-restore for PBS snapshots aderumier
2021-01-12 10:31 ` Thomas Lamprecht
2021-01-12 11:23 ` Thomas Lamprecht
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