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From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: Venki Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Paul Turner <pjt@google.com>, Ingo Molnar <mingo@elte.hu>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] sched: fix nohz idle load balancer issues
Date: Wed, 28 Sep 2011 19:47:01 +0530	[thread overview]
Message-ID: <20110928141701.GF8593@linux.vnet.ibm.com> (raw)
In-Reply-To: <20110928043427.GI4357@linux.vnet.ibm.com>

* Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> [2011-09-28 10:04:27]:

> > Especially with higher number of logical CPUs. Likely cleaner way is to clear
> > first_pick, second_pick on idle instead of clearing on tickless.
> 
> I think I tried that (cleared first/second_pick_cpu in
> nohz_kick_needed() upon idle) but didn't get the best results. Let me
> try that again and post idle time numbers.

So made some changes so that first/second_pick_cpu identifiers are
cleared when corresponding cpus become idle. They are cleared in
pick_next_task_idle() ..

With that change, I don't see additional benefit of having a third busy
cpu kick ilb_cpu when it has > 1 task.


Idle time -> 			Avg.	Std.Dev   Min   Max
W/o third busy cpu kicking	4.57%   0.9	  3%    8%   
With third busy cpu kicking	4.78%   1.1%      3%    8%

So will go with your suggestion in the next version!

- vatsa

  parent reply	other threads:[~2011-09-28 14:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-26 11:50 Srivatsa Vaddagiri
2011-09-26 12:01 ` Srivatsa Vaddagiri
2011-09-27  6:32 ` Ingo Molnar
2011-09-27 10:31   ` Srivatsa Vaddagiri
2011-09-27 13:39     ` Ingo Molnar
2011-09-27 19:53 ` Venki Pallipadi
2011-09-27 23:49   ` Suresh Siddha
2011-09-28  4:15     ` Srivatsa Vaddagiri
2011-09-29  0:47       ` Suresh Siddha
2011-09-29  2:13         ` Srivatsa Vaddagiri
2011-09-29  8:15         ` Peter Zijlstra
2011-09-29 17:13           ` Suresh Siddha
2011-09-28  4:34   ` Srivatsa Vaddagiri
2011-09-28  4:39     ` Srivatsa Vaddagiri
2011-09-28  5:06       ` Srivatsa Vaddagiri
2011-09-28 14:17     ` Srivatsa Vaddagiri [this message]
2011-09-28 14:27       ` Srivatsa Vaddagiri

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