linux-kernel - Re: [PATCH RFC] sched: boost throttled entities on wakeups

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Date:	Fri, 19 Oct 2012 16:24:50 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Vladimir Davydov <VDavydov@...allels.com>
Cc:	Ingo Molnar <mingo@...hat.com>, Paul Turner <pjt@...gle.com>,
	Kirill Korotaev <dev@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH RFC] sched: boost throttled entities on wakeups

On Thu, 2012-10-18 at 11:32 +0400, Vladimir Davydov wrote:
> 
> 1) Do you agree that the problem exists and should be sorted out?

This is two questions.. yes it exists, I'm absolutely sure I pointed it
out as soon as people even started talking about this nonsense (bw
cruft).

Should it be sorted, dunno, in general !PREEMPT_RT is very susceptible
to all this and in general we don't fix it.

> 2) If so, does the general approach proposed (unthrottling on wakeups) suits
> you? Why or why not?

its a quick hack similar to existing hacks done for rt, preferably we'd
do smarter things though.

> 3) If you think that the approach proposed is sane, what you dislike about the
> patch? 

its not inlined, its got coding style issues, but worst of all, you
added yet another callback from the schedule() path and did it wrong ;-)

Also, it adds even more bw cruft overhead to regular scheduling paths,
we took some pains to limit that when we introduced the fail^Wfeature.
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