Subject: Re: [RFC][PATCH] sched: fix GENTLE_FAIR_SLEEPERS dependency
From: Mike Galbraith <efault@gmx.de>
To: Suresh Jayaraman <sjayaraman@suse.de>
Cc: mingo@elte.hu, Peter Zijlstra <peterz@infradead.org>,
       LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <4B18D66E.8020905@suse.de>
References: <4B18D66E.8020905@suse.de>
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Date: Fri, 04 Dec 2009 11:06:27 +0100
Message-Id: <1259921187.15613.21.camel@marge.simson.net>
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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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