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Date: Mon, 16 May 2011 16:11:17 +0200 From: Mike Galbraith <efault@....de> To: Hillf Danton <dhillf@...il.com> Cc: LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>, Yong Zhang <yong.zhang0@...il.com>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH] sched: avoid overpull when pulling RT task On Mon, 2011-05-16 at 21:14 +0800, Hillf Danton wrote: > In the following patch, pulling is played in two rounds. In the first round, > the highest priority task is determined with no pull operation. Pulling is > carried out in the second round, and if the highest priority task is pulled, > pulling could be stopped when overload detected, to relieve overpull. > > Please review again, thanks. Traversing runqueues twice to avoid some potential task bouncing during overload situation seems like a really bad trade. Not to mention that between pass one and pass two, the world turns under your feet. You could do it in one pass by leaving the victim's runqueue locked unless you find a better victim I suppose. Dunno, guess it all depends on how much benefit the is to pulling only highest, which I can't answer (my gut says "none, only more pain to be had here"). -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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