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SubjectRe: [RFC PATCH 0/4] Gang scheduling in CFS
Date
On Tue, 27 Dec 2011 12:34:34 +0200, Avi Kivity <avi@redhat.com> wrote:
> On 12/27/2011 12:10 PM, Nikunj A Dadhania wrote:
> > On Tue, 27 Dec 2011 11:51:46 +0200, Avi Kivity <avi@redhat.com> wrote:
> > > On 12/27/2011 11:44 AM, Nikunj A Dadhania wrote:
> > > > > > I am seeing a drop of ~44% when setting yield_on_hlt = 0
> > > > > >
> > > > >
> > > > > A drop of 44% of what?
> > > > >
> > > > records/sec
> > > >
> > > > Ebizzy - 2VM running in parallel, both having gang scheduling enabled.
> > > >
> > > > yield_on_hlt=1 yield_on_hlt=0
> > > > EbzyRecords/sec 41955.50 23285.00 -44
> > > >
> > > >
> > >
> > > Interesting, are you overcommitting vcpus?
> > >
> > Yes(1:2). On a 8cpu machine, have 2VMs running, which is 8vcpus each.
>
> Ah, yield_on_hlt=0 isn't any good with overcommit. The vcpu stays
> scheduled when idle, so other vcpus don't get to use its cpu time.
>
This is similar to booting the guest with idle=poll kernel parameter?



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