linux-kernel - Re: [RFC][PATCH] sched: fix GENTLE_FAIR

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Message-Id: <1259921187.15613.21.camel@marge.simson.net>
Date:	Fri, 04 Dec 2009 11:06:27 +0100
From:	Mike Galbraith <efault@....de>
To:	Suresh Jayaraman <sjayaraman@...e.de>
Cc:	mingo@...e.hu, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] sched: fix GENTLE_FAIR_SLEEPERS dependency

On Fri, 2009-12-04 at 14:59 +0530, Suresh Jayaraman wrote:
> The newly introduced GENTLE_FAIR_SLEEPERS does not seem to have any
> effect without FAIR_SLEEPERS. Fix sysctl.sched_features to reflect
> this. Without this change, a user who sets GENTLE_FAIR_SLEEPERS
> without FAIR_SLEEPERS would assume gentle sleeper fairness which
> is not guaranteed.

IMHO, these dependencies belong in documentation, not enforcement code.

Same applies for LAST_BUDDY, meaningless without WAKEUP_PREEMPT.
SYNC_MORE, SYNC_LESS + AFFINE_WAKEUPS etc.

Bottom line for all button poking and knob turning is you'd better make
sure you know what button/knob does, and what other things may depend on
it before messing with it, lest you get a nasty surprise.

	-Mike

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