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

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Message-ID: <20120306100336.GB14298@linux.vnet.ibm.com>
Date:	Tue, 6 Mar 2012 15:33:36 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Turner <pjt@...gle.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible

* Ingo Molnar <mingo@...e.hu> [2012-03-06 10:14:11]:

> Does volanomark still do yield(),

I could count 3.5M yield() calls across 16 cpus over a period of 5.4sec,
so yes it does seem to make very good use of yeild()!

> thereby invoking a random 
> shuffle of thread scheduling and pretty much voluntarily 
> ejecting itself from most scheduler performance considerations?
> 
> If it uses a real locking primitive such as futexes then its 
> performance matters more.

Good point ..I will gather more data for additional benchmarks
(tbench, sysbench) and post shortly.

- vatsa

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