linux-kernel - Re: [PATCH v10 7/7] sched: Clean up load average references

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Date:	Mon, 27 Jul 2015 04:31:22 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Dietmar Eggemann <dietmar.eggemann@....com>
Cc:	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"pjt@...gle.com" <pjt@...gle.com>,
	"bsegall@...gle.com" <bsegall@...gle.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"umgwanakikbuti@...il.com" <umgwanakikbuti@...il.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"fengguang.wu@...el.com" <fengguang.wu@...el.com>
Subject: Re: [PATCH v10 7/7] sched: Clean up load average references

Hi Dietmar,

On Fri, Jul 24, 2015 at 05:41:45PM +0100, Dietmar Eggemann wrote:
> On 15/07/15 01:04, Yuyang Du wrote:
> > For cfs_rq, we have load.weight, runnable_load_avg, and load_avg. We
> > now start to clean up how they are used.
> > 
> > First, as group sched_entity already largely uses load_avg, we now expand
> > to use load_avg in all cases.
> 
> You're talking about group se's or cfs_rq owned by the group se's
> (se->my_q) here or both?
 
Definitely, group SE, and if the cfs_rq owned by group SE is also concerned
with group SE, then both. I don't think this is very well calculated to be 
optimal, but probably this is the right move I can think of now.

We need to revisit all of the codes before we can at least make a final call.

> Just asking because both data structures (cfs_rq and se) have a 'struct
> load_weight load' as well as 'struct sched_avg avg' member.
> 
>  Second, for CPU-wide load balancing, we
> > choose to use runnable_load_avg in all cases, which is the same as before
> > this series.
> 
> With your patch-set there will be still the difference of
> 'cfs_rq->utilization_load_avg' and your 'cfs_rq->avg.util_avg' in the
> sense that the former one does not contain the contribution of blocked se's.
> 
> The EAS patch-set adds blocked utilization contribution:
> https://lkml.org/lkml/2015/7/7/915
> 
> The cfs_rq utilization is also used by the load-balancer code via
> get_cpu_usage() so the blocked utilization contribution to
> 'cfs_rq->avg.util_avg' can change load-balancing as well.
> 
> Since it is not as heavily used as the cfs_rq->runnable_load_avg we
> might not need to reintroduce cfs_rq->utilization_load_avg but at least
> mention this here.
> 

Yes, thanks.
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