linux-kernel - Re: sched: Avoid SMT siblings in select_idle

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Date:	Thu, 23 Feb 2012 16:19:59 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible

* Mike Galbraith <efault@....de> [2012-02-20 19:14:21]:

> > I was looking at this code due to vatsa wanting to do SD_BALANCE_WAKE.
> 
> I really really need to find time to do systematic mainline testing.
> 
> Enabling SD_BALANCE_WAKE used to be decidedly too expensive to consider.
> Maybe that has changed, but I doubt it.  (general aside: testing with a
> bloated distro config is a big mistake)

I am seeing 2.6% _improvement_ in volanomark score by enabling SD_BALANCE_WAKE 
at SMT/MC domains.

Machine : 2 Quad-core Intel X5570 CPU (H/T enabled)
Kernel  : tip (HEAD at 6241cc8)
Java	: OpenJDK 1.6.0_20
Volano  : 2_9_0

Volano benchmark was run 4 times with and w/o SD_BALANCE_WAKE enabled in
SMT/MC domains.

				Average score	std. dev

SD_BALANCE_WAKE disabled	369459.750	4825.046
SD_BALANCE_WAKE enabled		379070.500	379070.5

I am going to try pipe benchmark next. Do you have suggestions for any other 
benchmarks I should try to see the effect of SD_BALANCE_WAKE turned on in 
SMT/MC domains?

- vatsa

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