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

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Date:	Mon, 02 Jan 2012 15:52:40 +0530
From:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.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 Mon, 02 Jan 2012 11:39:00 +0200, Avi Kivity <avi@...hat.com> wrote:
> On 01/02/2012 06:20 AM, Nikunj A Dadhania wrote:
[...]
> > >     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... 
>
Getting similar numbers across different runs/reboots with dbench.

> what happens if you add a bash
> busy loop?
> 
Perf output for bash busy loops inside the guest:

     9.93%           sh  libc-2.12.so       [.] _int_free
     8.37%           sh  libc-2.12.so       [.] _int_malloc
     6.14%           sh  libc-2.12.so       [.] __GI___libc_malloc
     6.03%           sh  bash               [.] 0x480e6         


loop.sh
----------------------------------
for i in `seq 1 8`
do
	while :; do :; done &
	pid[$i]=$!;
done
sleep 60

for i in `seq 1 8`
do
	kill -9 ${pid[$i]}
done
----------------------------------

Used the following command to capture the perf events inside the guest:

ssh root@....168.123.11 'perf record -a -o loop-perf.out  --
/root/loop.sh '

Regards,
Nikunj

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