linux-kernel - Re: [PATCH v1 00/10] Optimize sched avgs computation and implement flat util hierarchy

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Date:	Wed, 10 Aug 2016 08:23:52 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	matt@...eblueprint.co.uk, umgwanakikbuti@...il.com
Subject: Re: [PATCH v1 00/10] Optimize sched avgs computation and implement
 flat util hierarchy

On Wed, Aug 10, 2016 at 08:14:45AM +0800, Yuyang Du wrote:
> Hi Peter,
> 
> I should have sent out my flat util hierarchy implementation long time ago,
> actually code was there but not rebased. I finally have time to do this,
> so here it is. There are also other proposals to solve migrated tasks' util
> mobility problem, such as the ones from Dietmar and Vincent.
> 
> The sched avgs computation optimization was initiated for the flat util thing,
> so I send them out together.
> 
> According to Morten and Ben's feedback, I removed 32-bit as a period's upper
> bound limit. So, thanks a lot to them.
> 

To compare the effectiveness of the flat util hierarchy, a simple experiment
was done: rt-app to generate a 50% duty-cycling workload (100us/200us), and
in the meantime a script to set the CPU affinity of the task, alternating
to taskset the task to run on CPU x and CPU y every 0.3 sec, so forcing the
task to ping-pong migrate. By auto-group and ssh itself, the task under test
is at the third level task group.

So compare the top cfs_rq's util_avg (group_hierarchy.jpg) vs. the rq's util_avg
(flat_hierarchy.jpg)

Thanks,
Yuyang

Download attachment "group_hierarchy.jpg" of type "image/jpeg" (48406 bytes)

Download attachment "flat_hierarchy.jpg" of type "image/jpeg" (32646 bytes)