linux-kernel - Re: [PATCH 5/5] sched/rt: Optimize find_lowest

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Date:	Thu, 29 Jan 2015 12:17:39 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Xunlei Pang <pang.xunlei@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH 5/5] sched/rt: Optimize find_lowest_rq() to select a
 cache hot cpu

On Fri, 30 Jan 2015 00:42:47 +0800
Xunlei Pang <pang.xunlei@...aro.org> wrote:

 
> I think the responsiveness is the most important feature for RT tasks,
> so I think:
> response latency > cache > SMT in significance.

Unfortunately, sometimes cache affects response latency.

> 
> I was wondering if we can take the cpuidle state into account like
> current find_idlest_cpu() for CFS?
> cpupri_find() can be easily modified to indicate the CPUPRI_IDLE case,
> then we can select
> an optimal idle cpu to improve RT tasks' responsiveness. For other
> cases(mostly non-idle cpu),

Even if that idle cpu happens to be on another NUMA node?

-- Steve

> I think we can rely on the existent sched_domain iteraction to select
> a cache-hot cpu without
> caring too much about SMT.


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