linux-kernel - Re: [PATCH 4/5] sched: don't consider upper se in sched

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Date:	Fri, 5 Apr 2013 11:06:43 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Mike Galbraith <efault@....de>,
	Paul Turner <pjt@...gle.com>, Alex Shi <alex.shi@...el.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 4/5] sched: don't consider upper se in sched_slice()

Hello, Preeti.

On Thu, Apr 04, 2013 at 12:18:32PM +0530, Preeti U Murthy wrote:
> Hi Joonsoo,
> 
> On 04/04/2013 06:12 AM, Joonsoo Kim wrote:
> > Hello, Preeti.
> 
> > 
> > So, how about extending a sched_period with rq->nr_running, instead of
> > cfs_rq->nr_running? It is my quick thought and I think that we can ensure
> > to run atleast once in this extending sched_period.
> 
> Yeah this seems to be correct.This would ensure sched_min_granularity
> also. So then in the scenarion where there are 2 tgs in a runqueue with
> 10 tasks each,when we calculate the sched_slice of any task,the
> __sched_period() would return 4*20 = 80ms.
> 
> The sched_slice of each of the task would be 80/20 = 4ms. But what about
> the sched_slice of each task group? How would that be calculated then?

Ah... Okay.
I will think more deeply about this issue.

> 
> Let us take the above example and walk through this problem.This would
> probably help us spot the issues involved with this.
> 
> > And, do we leave a problem if we cannot guaranteed atleast once property?
> 
> This would depend on the results of the benchmarks with the changes.I am
> unable to comment on this off the top of my head.

Okay. :)

Thanks for your kind review!!

> 
> Thank you
> 
> Regards
> Preeti U Murthy
> 
> 
> 
> 
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