linux-kernel - Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinned

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Date:	Wed, 8 Jun 2011 14:46:06 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
CC:	Paul Turner <pjt@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelianov <xemul@...allels.com>
Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned
	vs unpinned

On Tue, 2011-06-07 at 19:45 +0400, Kamalesh Babulal wrote:
> Hi All,
> 
>     In our test environment, while testing the CFS Bandwidth V6 patch set
> on top of 55922c9d1b84. We observed that the CPU's idle time is seen
> between 30% to 40% while running CPU bound test, with the cgroups tasks
> not pinned to the CPU's. Whereas in the inverse case, where the cgroups
> tasks are pinned to the CPU's, the idle time seen is nearly zero.

(snip)

> load_tasks()
> {
>         for (( i=1; i<=5; i++ ))
>         do
>                 jj=$(eval echo "\$NR_TASKS$i")
>                 shares="1024"
>                 if [ $PRO_SHARES -eq 1 ]
>                 then
>                         eval shares=$(echo "$jj * 1024" | bc)
>                 fi
>                 echo $hares > $MOUNT/$i/cpu.shares
                        ^^^^^
                        a fatal misprint? must be shares, I guess

(Setting cpu.shares to "", i.e. to the minimal possible value, will
definitely confuse the load balancer)

>                 for (( j=1; j<=$jj; j++ ))
>                 do
>                         echo "-1" > $MOUNT/$i/cpu.cfs_quota_us
>                         echo "500000" > $MOUNT/$i/cpu.cfs_period_us
>                         if [ $SUBGROUP -eq 1 ]
>                         then
> 
>                                 $LOAD &
>                                 echo $! > $MOUNT/$i/$j/tasks
>                                 echo "1024" > $MOUNT/$i/$j/cpu.shares
> 
>                                 if [ $BANDWIDTH -eq 1 ]
>                                 then
>                                         echo "500000" > $MOUNT/$i/$j/cpu.cfs_period_us
>                                         echo "250000" > $MOUNT/$i/$j/cpu.cfs_quota_us
>                                 fi
>                         else
>                                 $LOAD &
>                                 echo $! > $MOUNT/$i/tasks
>                                 echo $shares > $MOUNT/$i/cpu.shares
> 
>                                 if [ $BANDWIDTH -eq 1 ]
>                                 then
>                                         echo "500000" > $MOUNT/$i/cpu.cfs_period_us
>                                         echo "250000" > $MOUNT/$i/cpu.cfs_quota_us
>                                 fi
>                         fi
>                 done
>         done
>         echo "Captuing idle cpu time with vmstat...."
>         vmstat 2 100 &> vmstat_log &
> }


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