linux-kernel - Re: [RFCv3 PATCH 18/48] sched: Track blocked utilization contributions

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Date:	Tue, 24 Mar 2015 17:44:09 +0000
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"mingo@...hat.com" <mingo@...hat.com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	"yuyang.du@...el.com" <yuyang.du@...el.com>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"mturquette@...aro.org" <mturquette@...aro.org>,
	"nico@...aro.org" <nico@...aro.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <Juri.Lelli@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFCv3 PATCH 18/48] sched: Track blocked utilization
 contributions

On Tue, Mar 24, 2015 at 04:07:29PM +0000, Peter Zijlstra wrote:
> On Tue, Mar 24, 2015 at 09:43:47AM +0000, Morten Rasmussen wrote:
> > On Mon, Mar 23, 2015 at 02:08:01PM +0000, Peter Zijlstra wrote:
> > > On Wed, Feb 04, 2015 at 06:30:55PM +0000, Morten Rasmussen wrote:
> > > > Introduces the blocked utilization, the utilization counter-part to
> > > > cfs_rq->utilization_load_avg. It is the sum of sched_entity utilization
> > > > contributions of entities that were recently on the cfs_rq that are
> > > > currently blocked. Combined with sum of contributions of entities
> > > > currently on the cfs_rq or currently running
> > > > (cfs_rq->utilization_load_avg) this can provide a more stable average
> > > > view of the cpu usage.
> > > 
> > > So it would be nice if you add performance numbers for all these patches
> > > that add accounting muck.. 
> > 
> > Total scheduler latency (as in hackbench?), individual function
> > latencies, or something else?
> 
> Yeah, good question that. Something that is good at running this code a
> lot. So dequeue_entity() -> dequeue_entity_load_avg() ->
> update_entity_load_avg() -> __update_entity_runnable_avg() seems a
> reliable way into here, and IIRC hackbench does a lot of that, so yes,
> that might just work.

Hackbench does a lot of that. I used it recently to measure the impact
of the weak arch_scale_*() functions. I will dig out some numbers.
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