linux-kernel - Re: [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE

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Date:	Thu, 28 May 2015 17:25:37 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Josef Bacik <jbacik@...com>
Cc:	riel@...hat.com, mingo@...hat.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for
 BALANCE_WAKE

> At Facebook we have a pretty heavily multi-threaded application that is
> sensitive to latency.  We have been pulling forward the old SD_WAKE_IDLE code
> because it gives us a pretty significant performance gain (like 20%).  It turns
> out this is because there are cases where the scheduler puts our task on a busy
> CPU when there are idle CPU's in the system.  We verify this by reading the
> cpu_delay_req_avg_us from the scheduler netlink stuff.  With our crappy patch we
> get much lower numbers vs baseline.
>

Was this application run under cpu cgroup. Because we were seeing bursty
workloads exhibiting this behaviour esp when run under cpu cgroups.

http://mid.gmane.org/53A11A89.5000602@linux.vnet.ibm.com

-- 
Thansk and Regards
Srikar

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