linux-kernel - Re: [PATCH -v2 02/18] sched/fair: Add comment to calc_cfs

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Date:   Fri, 29 Sep 2017 14:03:36 +0100
From:   Morten Rasmussen <morten.rasmussen@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, tj@...nel.org,
        josef@...icpanda.com, torvalds@...ux-foundation.org,
        vincent.guittot@...aro.org, efault@....de, pjt@...gle.com,
        clm@...com, dietmar.eggemann@....com, bsegall@...gle.com,
        yuyang.du@...el.com
Subject: Re: [PATCH -v2 02/18] sched/fair: Add comment to calc_cfs_shares()

On Fri, Sep 29, 2017 at 01:35:00PM +0200, Peter Zijlstra wrote:
> On Thu, Sep 28, 2017 at 11:03:03AM +0100, Morten Rasmussen wrote:
> > IIUC, if grq->avg.load_avg > grq->load.weight, i.e. you have blocked
> > tasks, you can end up with underestimating the ge->load.weight for some
> > of the group entities lead to \Sum ge->load.weight < tg->weight.
> 
> Ah yes, you're right. However, if you look at the end of the series we
> actually end up with using:
> 
> 	max(grq->load.weight, grq->avg.load_avg)
> 
> Which I suppose makes it true again.

Yes, with the next patch in the series, underestimation is no longer
possible.