From: Thomas Lamprecht <t.lamprecht@proxmox.com>
To: Elias Huhsovitz <e.huhsovitz@proxmox.com>,
Markus Frank <m.frank@proxmox.com>,
pve-devel@lists.proxmox.com
Subject: Re: [PATCH qemu-server v1] {pbs-,vma-}restore: disable caching for LVM-thin
Date: Mon, 9 Nov 2026 17:12:40 +0100 [thread overview]
Message-ID: <72e56f92-b00b-4835-874d-c8fce2298619@proxmox.com> (raw)
In-Reply-To: <DLMMW8NCI0RY.1QDRTI5M2G25Z@proxmox.com>
Am 23.09.26 um 12:46 schrieb Elias Huhsovitz:
> Thanks for spotting this potential optimization.
> Gave this quick try and results seem to be mixed.
>
> When restoring from a pbs I saw a time reduction of ~35%.
> When restoring locally from a .vma.zst file i saw a time increase of
> ~81%.
Might be due to us triggering 64 KiB writes on VMA, which can get
coalesced if caching is active thus papering over the non-ideal IO
behavior from us there. Without cache the storage sees each such
request explicitly, causing more IO operations. This should be
improved with [0] which coalesces the requests directly in VMA, thus
reducing amount of syscalls (not really relevant on such IO heavy
workloads) due to submitting up to a full extent of 58 x 64 KiB
clusters – so 3.6 MiB – in one go.
[0]: https://lore.proxmox.com/pve-devel/20261109160210.3380582-1-t.lamprecht@proxmox.com/
prev parent reply other threads:[~2026-11-09 16:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-08 12:37 [PATCH qemu-server v1] {pbs-,vma-}restore: disable caching for LVM-thin Markus Frank
2026-09-23 10:46 ` Elias Huhsovitz
2026-11-09 16:12 ` Thomas Lamprecht [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=72e56f92-b00b-4835-874d-c8fce2298619@proxmox.com \
--to=t.lamprecht@proxmox.com \
--cc=e.huhsovitz@proxmox.com \
--cc=m.frank@proxmox.com \
--cc=pve-devel@lists.proxmox.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.