linux-kernel - Re: [RFC][PATCH 1/7] sched: Replace post_schedule with a balance callback list

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Message-ID: <20150605071931.GB19282@twins.programming.kicks-ass.net>
Date:	Fri, 5 Jun 2015 09:19:31 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	pang.xunlei@....com.cn
Cc:	juri.lelli@...il.com, ktkhai@...allels.com,
	linux-kernel@...r.kernel.org, mingo@...e.hu, oleg@...hat.com,
	pang.xunlei@...aro.org, rostedt@...dmis.org,
	umgwanakikbuti@...il.com
Subject: Re: [RFC][PATCH 1/7] sched: Replace post_schedule with a balance
 callback list

On Fri, Jun 05, 2015 at 03:13:38PM +0800, pang.xunlei@....com.cn wrote:
> > It will make sched_setscheduler() etc.. a little more expensive, but
> > that doesn't matter, those are not critical things at all.
> 
> Another side effect it may have is that it will introduce some latency, 
> because we have to wait for next schedule() point to do the balancing. 
> prio_changed_rt()->pull_rt_task() is not rare cases when using PI futex.

See patch 3, that adds the balance_callback() to sched_setscheduler()
and rt_mutex_setprio() to avoid just that.

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