linux-kernel - Re: sched: tweak select_idle_sibling to look for idle threads

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Message-ID: <1462866562.3702.33.camel@suse.de>
Date:	Tue, 10 May 2016 09:49:22 +0200
From:	Mike Galbraith <mgalbraith@...e.de>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Chris Mason <clm@...com>,
	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: sched: tweak select_idle_sibling to look for idle threads

On Tue, 2016-05-10 at 07:26 +0800, Yuyang Du wrote:

> By cpu reservation, you mean the various averages in select_task_rq_fair?
> It does seem a lot of cleanup should be done.

Nah, I meant claiming an idle cpu with cmpxchg().  It's mostly the
average load business that leads to premature stacking though, the
reservation thingy more or less just wastes cycles.  Only whacking
cfs_rq_runnable_load_avg() with a rock makes schbench -m <sockets> -t
<near socket size> -a work well.  'Course a rock in its gearbox also
rendered load balancing fairly busted for the general case :)

	-Mike