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

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Date:	Wed, 04 Jan 2012 16:41:58 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
CC:	Rik van Riel <riel@...hat.com>, 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 01/04/2012 12:52 PM, Nikunj A Dadhania wrote:
> On Mon, 02 Jan 2012 11:37:22 +0200, Avi Kivity <avi@...hat.com> wrote:
> > On 12/31/2011 04:21 AM, Nikunj A Dadhania wrote:
> > >
> > >     GangV2:
> > >     27.45%       ebizzy  libc-2.12.so            [.] __memcpy_ssse3_back
> > >     12.12%       ebizzy  [kernel.kallsyms]       [k] clear_page
> > >      9.22%       ebizzy  [kernel.kallsyms]       [k] __do_page_fault
> > >      6.91%       ebizzy  [kernel.kallsyms]       [k] flush_tlb_others_ipi
> > >      4.06%       ebizzy  [kernel.kallsyms]       [k] get_page_from_freelist
> > >      4.04%       ebizzy  [kernel.kallsyms]       [k] ____pagevec_lru_add
> > >
> > >     GangBase:
> > >     45.08%       ebizzy  [kernel.kallsyms]       [k] flush_tlb_others_ipi
> > >     15.38%       ebizzy  libc-2.12.so            [.] __memcpy_ssse3_back
> > >      7.00%       ebizzy  [kernel.kallsyms]       [k] clear_page
> > >      4.88%       ebizzy  [kernel.kallsyms]       [k] __do_page_fault
> > 
> > Looping in flush_tlb_others().  Rik, what trace an we run to find out
> > why PLE directed yield isn't working as expected?
> > 
> I tried some experiments by adding a pause_loop_exits stat in the
> kvm_vpu_stat.

(that's deprecated, we use tracepoints these days for stats)

> Here are some observation related to Baseline-only(8vm case)
>
>               | ple_gap=128 | ple_gap=64 | ple_gap=256 | ple_window=2048
> --------------+-------------+------------+-------------+----------------
> EbzyRecords/s |    2247.50  |    2132.75 |    2086.25  |      1835.62
> PauseExits    | 7928154.00  | 6696342.00 | 7365999.00  |  50319582.00
>
> With ple_window = 2048, PauseExits is more than 6times the default case

So it looks like the default is optimal, at least wrt the cases you
tested and your test workload.

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

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