From: Atila Vasconcelos <atilav@lightspeed.ca>
To: pve-user@lists.proxmox.com
Subject: Re: [PVE-User] linux idle cpu overhead in kvm - old issue, but still there in 2020...
Date: Tue, 14 Jul 2020 09:05:43 -0700 [thread overview]
Message-ID: <a51ea111-c782-0d35-a801-d8f659ddbfd9@lightspeed.ca> (raw)
In-Reply-To: <4900ba10-107e-439c-9716-6e988ae7f5ef@web.de>
Wow, I just tried this at my servers (very old Dell PowerEdge 2950);
The results are impressive!
8o
ABV
On 2020-07-13 3:15 a.m., Roland wrote:
> 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
>
>
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> pve-user mailing list
> pve-user@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
>
next prev parent reply other threads:[~2020-07-14 16:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 10:15 Roland
2020-07-14 16:05 ` Atila Vasconcelos [this message]
2020-07-14 17:16 ` Roland
[not found] ` <79fb6f58-0d41-80da-4bfa-2cdc344a3245@web.de>
2020-07-18 13:02 ` Roland
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