From: Roland <devzero@web.de>
To: PVE User List <pve-user@pve.proxmox.com>
Subject: [PVE-User] linux idle cpu overhead in kvm - old issue, but still there in 2020...
Date: Mon, 13 Jul 2020 12:15:23 +0200 [thread overview]
Message-ID: <4900ba10-107e-439c-9716-6e988ae7f5ef@web.de> (raw)
hello,
i have found that there is an old bug still around in linux, which is
causing quite an amount of unnecessary cpu consumption in kvm/proxmox,
and thus, wasting precious power.
i run some proxmox installations on older systems and on those, it's
quite significant difference.
on the slowest system, a single debian 10 VM , kvm process is at 20% cpu
(VM is 100% idle) when this issue is present.
if i change VMs machine type from i440fx(default) to q35 the problem
goes away.
the same applies when running "powertop --auto-tune" inside the guest
(with i440fx type - enable autosuspend for usb-controller + tablet device).
on some L5630 machine, in proxmox summary i see "CPU usage" drop from
10% to <1%.
see:
https://bugzilla.redhat.com/show_bug.cgi?id=478317
https://bugzilla.redhat.com/show_bug.cgi?id=949547
i guess this information could make a difference for people who run a
large amount of virtual machines or use older systems/cpu's.
on most recent cpu's, i think the difference is not that big.
anyway, i really wonder how linux bugs have such great survival
capability....
regards
roland
more references:
https://lists.gnu.org/archive/html/qemu-devel/2010-04/msg00149.html
https://www.redhat.com/archives/vfio-users/2015-November/msg00159.html
next reply other threads:[~2020-07-13 10:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 10:15 Roland [this message]
2020-07-14 16:05 ` Atila Vasconcelos
2020-07-14 17:16 ` Roland
[not found] ` <79fb6f58-0d41-80da-4bfa-2cdc344a3245@web.de>
2020-07-18 13:02 ` Roland
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=4900ba10-107e-439c-9716-6e988ae7f5ef@web.de \
--to=devzero@web.de \
--cc=pve-user@pve.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.