From: Thomas Lamprecht <t.lamprecht@proxmox.com>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>,
Fiona Ebner <f.ebner@proxmox.com>
Subject: [pve-devel] applied: [PATCH qemu] async snapshot: stop vCPU throttling after finishing
Date: Sun, 10 Nov 2024 11:24:29 +0100 [thread overview]
Message-ID: <93c7df0e-7311-4138-bb9c-9b98768db8c4@proxmox.com> (raw)
In-Reply-To: <20241030095240.11452-1-f.ebner@proxmox.com>
Am 30.10.24 um 10:52 schrieb Fiona Ebner:
> In the community forum, users reported issues about RCU stalls and
> sluggish VMs after taking a snapshot with RAM in Proxmox VE [0]. Mario
> was also experiencing similar issues from time to time and recently,
> obtained a GDB stacktrace. The stacktrace showed that, in his case,
> the vCPU threads were waiting in cpu_throttle_thread(). It is a good
> guess that the issues in the forum could also be because of that.
>
> From searching in the source code, it seems that migration is the only
> user of the vCPU throttling functions in QEMU relevant for Proxmox VE
> (the only other place where it is used is the Cocoa UI). In
> particular, RAM migration will begin throttling vCPUs for
> auto-converge.
>
> In migration_iteration_finish() there is an unconditional call to
> cpu_throttle_stop(), so do the same in the async snapshot code
> specific to Proxmox VE.
>
> It's not clear why the issue began to surface more prominently only
> now, since the vCPU throttling was there since commit 070afca258
> ("migration: Dynamic cpu throttling for auto-converge") in QEMU
> v2.10.0. However, there were a lot of changes in the migration code
> between v8.1.5 and v9.0.2 and a few of them might have affected the
> likelihood of cpu_throttle_set() being called, for example, 4e1871c450
> ("migration: Don't serialize devices in qemu_savevm_state_iterate()")
>
> [0]: https://forum.proxmox.com/threads/153483
>
> Reported-by: Mario Loderer <m.loderer@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> Tested-by: Mario Loderer <m.loderer@proxmox.com>
> ---
> ...-async-for-background-state-snapshots.patch | 18 +++++++++++++-----
> ...-add-optional-buffer-size-to-QEMUFile.patch | 6 +++---
> 2 files changed, 16 insertions(+), 8 deletions(-)
>
>
applied, thanks!
_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
prev parent reply other threads:[~2024-11-10 10:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-30 9:52 [pve-devel] " Fiona Ebner
2024-11-08 15:18 ` Fiona Ebner
2024-11-10 10:24 ` 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=93c7df0e-7311-4138-bb9c-9b98768db8c4@proxmox.com \
--to=t.lamprecht@proxmox.com \
--cc=f.ebner@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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox