From: Roland <devzero@web.de>
To: Proxmox VE user list <pve-user@lists.proxmox.com>,
Atila Vasconcelos <atilav@lightspeed.ca>
Subject: Re: [PVE-User] linux idle cpu overhead in kvm - old issue, but still there in 2020...
Date: Tue, 14 Jul 2020 19:16:40 +0200 [thread overview]
Message-ID: <84b3b8ca-80f8-94d0-27c7-899743ac08e1@web.de> (raw)
In-Reply-To: <a51ea111-c782-0d35-a801-d8f659ddbfd9@lightspeed.ca>
nice :)
what guest OS do you use and which showed the problem ?
as i think that q35 will not be default in kvm or proxmox anytime soon,
shouldn't we perhaps file a bug report for every distro affected ?
is there someone who likes to work with this (help testing,
writing/tracking bug reports...) ?
could perhaps save some tons of CO2 ....
roland
Am 14.07.20 um 18:05 schrieb Atila Vasconcelos:
> 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
>>
>>
>> _______________________________________________
>> pve-user mailing list
>> pve-user@lists.proxmox.com
>> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
>>
>
> _______________________________________________
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>
next prev parent reply other threads:[~2020-07-14 17:22 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
2020-07-14 17:16 ` Roland [this message]
[not found] ` <79fb6f58-0d41-80da-4bfa-2cdc344a3245@web.de>
2020-07-18 13:02 ` Roland
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