linux-kernel - Re: [RFC PATCH 0/4] Gang scheduling in CFS

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Message-ID: <4F017B34.109@redhat.com>
Date:	Mon, 02 Jan 2012 11:39:00 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
CC:	Ingo Molnar <mingo@...e.hu>, peterz@...radead.org,
	linux-kernel@...r.kernel.org, vatsa@...ux.vnet.ibm.com,
	bharata@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS

On 01/02/2012 06:20 AM, Nikunj A Dadhania wrote:
> On Sat, 31 Dec 2011 07:51:15 +0530, Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com> wrote:
> > On Fri, 30 Dec 2011 15:40:06 +0530, Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com> wrote:
> > > On Fri, 30 Dec 2011 10:51:47 +0100, Ingo Molnar <mingo@...e.hu> wrote:
> > > > 
> > > > * Avi Kivity <avi@...hat.com> wrote:
> > > > 
> > > > > [...]
> > > > > 
> > > > > The first part appears to be unrelated to ebizzy itself - it's 
> > > > > the kunmap_atomic() flushing ptes.  It could be eliminated by 
> > > > > switching to a non-highmem kernel, or by allocating more PTEs 
> > > > > for kmap_atomic() and batching the flush.
> > > > 
> > > > Nikunj, please only run pure 64-bit/64-bit combinations - by the 
> > > > time any fix goes upstream and trickles down to distros 32-bit 
> > > > guests will be even less relevant than they are today.
> > > > 
> > > Sure Ingo, got a 64bit guest working yesterday and I am in process of
> > > getting the benchmark numbers for the same.
> > > 
> > Here is the results collected from the 64bit VM runs. 
> > 
> [...]
>
> PLE worst case:
>
> >      
> >     dbench 8vm (degraded -8%)
> >     |      dbench|               2.27 |               2.09 |       -8 |
> [...]
> >     dbench needs some more love, i will get the perf top caller for
> >     that.
> >
>
>     Baseline:
>     75.18%         init  [kernel.kallsyms]  [k] native_safe_halt
>     23.32%      swapper  [kernel.kallsyms]  [k] native_safe_halt
>
>     Gang V2:
>     73.21%         init  [kernel.kallsyms]       [k] native_safe_halt
>     25.74%      swapper  [kernel.kallsyms]       [k] native_safe_halt
>
> That does not give much clue :(
> Comments?
>
> >     non-PLE - Test Setup:
> > 
> >     dbench 8vm (degraded -30%)
> >     |      dbench|               2.01 |               1.38 |      -30 |
>
>
>     Baseline:
>     57.75%         init  [kernel.kallsyms]  [k] native_safe_halt
>     40.88%      swapper  [kernel.kallsyms]  [k] native_safe_halt
>
>     Gang V2:
>     56.25%         init  [kernel.kallsyms]  [k] native_safe_halt
>     42.84%      swapper  [kernel.kallsyms]  [k] native_safe_halt
>
> Similar comparison here.
>

Wierd, looks like a mismeasurement... what happens if you add a bash
busy loop?

-- 
error compiling committee.c: too many arguments to function

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