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

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Message-ID: <1329816093.7333.49.camel@marge.simpson.net>
Date:	Tue, 21 Feb 2012 10:21:33 +0100
From:	Mike Galbraith <efault@....de>
To:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
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

On Tue, 2012-02-21 at 14:02 +0530, Srivatsa Vaddagiri wrote: 
> * Mike Galbraith <efault@....de> [2012-02-21 06:43:18]:
> 
> > On Mon, 2012-02-20 at 20:07 +0100, Peter Zijlstra wrote: 
> > > On Mon, 2012-02-20 at 19:14 +0100, Mike Galbraith wrote:
> > > > Enabling SD_BALANCE_WAKE used to be decidedly too expensive to consider.
> > > > Maybe that has changed, but I doubt it.
> > > 
> > > Right, I through I remembered some such, you could see it on wakeup
> > > heavy things like pipe-bench and that java msg passing thing, right?
> > 
> > Yeah, it beat up switch heavy buddies pretty bad.
> 
> Do you have pointer to the java benchmark? Also is pipe-bench the same
> as the one described below?

I use vmark, find it _somewhat_ useful.  Not a lovely benchmark, but it
is highly affinity sensitive, and switches heftily.  I don't put much
value on it though, too extreme for me, but it is a ~decent indicator.

There are no doubt _lots_ better than vmark for java stuff.

I toss a variety pack at the box in obsessive-compulsive man mode when
testing.  Which benchmarks doesn't matter much, just need to be wide
spectrum and consistent.

> http://freecode.com/projects/pipebench

No, I use Ingo's pipe-test, but that to measure fastpath overhead.

-Mike

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