* default elevator=noop for virtio block devices?
@ 2011-03-09 9:42 Harald Dunkel
2011-03-09 10:01 ` Avi Kivity
0 siblings, 1 reply; 4+ messages in thread
From: Harald Dunkel @ 2011-03-09 9:42 UTC (permalink / raw)
To: KVM Mailing List
Hi folks,
would it make sense to make elevator=noop the default
for virtio block devices? Or would you recommend to
set this on the kvm server instead?
Any helpful comment would be highly appreciated
Harri
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: default elevator=noop for virtio block devices?
2011-03-09 9:42 default elevator=noop for virtio block devices? Harald Dunkel
@ 2011-03-09 10:01 ` Avi Kivity
2011-03-09 11:12 ` Stefan Hajnoczi
0 siblings, 1 reply; 4+ messages in thread
From: Avi Kivity @ 2011-03-09 10:01 UTC (permalink / raw)
To: Harald Dunkel; +Cc: KVM Mailing List
On 03/09/2011 11:42 AM, Harald Dunkel wrote:
> Hi folks,
>
> would it make sense to make elevator=noop the default
> for virtio block devices? Or would you recommend to
> set this on the kvm server instead?
>
I think leaving the defaults is best. The elevator on the guest serves
to schedule I/O among processes in the guest, and the elevator on the
host partitions I/O among the guests.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: default elevator=noop for virtio block devices?
2011-03-09 10:01 ` Avi Kivity
@ 2011-03-09 11:12 ` Stefan Hajnoczi
2011-03-09 14:47 ` Khoa Huynh
0 siblings, 1 reply; 4+ messages in thread
From: Stefan Hajnoczi @ 2011-03-09 11:12 UTC (permalink / raw)
To: Harald Dunkel; +Cc: KVM Mailing List, Khoa Huynh, Avi Kivity
On Wed, Mar 9, 2011 at 10:01 AM, Avi Kivity <avi@redhat.com> wrote:
> On 03/09/2011 11:42 AM, Harald Dunkel wrote:
>>
>> Hi folks,
>>
>> would it make sense to make elevator=noop the default
>> for virtio block devices? Or would you recommend to
>> set this on the kvm server instead?
>>
>
> I think leaving the defaults is best. The elevator on the guest serves to
> schedule I/O among processes in the guest, and the elevator on the host
> partitions I/O among the guests.
It depends on the workload. Khoa has seen cases where CFQ does not
scale with multi-threaded workloads and deadline is preferred. But
it's not one-size-fits-all, it depends on your workload and requires
benchmarking.
Stefan
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: default elevator=noop for virtio block devices?
2011-03-09 11:12 ` Stefan Hajnoczi
@ 2011-03-09 14:47 ` Khoa Huynh
0 siblings, 0 replies; 4+ messages in thread
From: Khoa Huynh @ 2011-03-09 14:47 UTC (permalink / raw)
To: Stefan Hajnoczi; +Cc: Avi Kivity, Harald Dunkel, KVM Mailing List
Stefan Hajnoczi <stefanha@gmail.com> wrote on 03/09/2011 05:12:07 AM:
>
> On Wed, Mar 9, 2011 at 10:01 AM, Avi Kivity <avi@redhat.com> wrote:
> > On 03/09/2011 11:42 AM, Harald Dunkel wrote:
> >>
> >> Hi folks,
> >>
> >> would it make sense to make elevator=noop the default
> >> for virtio block devices? Or would you recommend to
> >> set this on the kvm server instead?
> >>
> >
> > I think leaving the defaults is best. The elevator on the guest serves
to
> > schedule I/O among processes in the guest, and the elevator on the host
> > partitions I/O among the guests.
>
> It depends on the workload. Khoa has seen cases where CFQ does not
> scale with multi-threaded workloads and deadline is preferred. But
> it's not one-size-fits-all, it depends on your workload and requires
> benchmarking.
Yes, for I/O-intensive workloads on fast storage systems, I've found
that the deadline scheduler works best.
Thanks,
-Khoa
^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-03-09 9:42 default elevator=noop for virtio block devices? Harald Dunkel
2011-03-09 10:01 ` Avi Kivity
2011-03-09 11:12 ` Stefan Hajnoczi
2011-03-09 14:47 ` Khoa Huynh
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