linux-kernel - Re: [Patch v4 4/6] sched/fair: update cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 31 Oct 2019 10:53:43 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thara Gopinath <thara.gopinath@...aro.org>, mingo@...hat.com,
        ionela.voinescu@....com, vincent.guittot@...aro.org,
        rui.zhang@...el.com, edubezval@...il.com, qperret@...gle.com,
        linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, daniel.lezcano@...aro.org
Subject: Re: [Patch v4 4/6] sched/fair: update cpu_capcity to reflect thermal
 pressure

On 10/28/19 16:30, Peter Zijlstra wrote:
> On Wed, Oct 23, 2019 at 01:28:40PM +0100, Qais Yousef wrote:
> > On 10/22/19 16:34, Thara Gopinath wrote:
> > > cpu_capacity relflects the maximum available capacity of a cpu. Thermal
> > > pressure on a cpu means this maximum available capacity is reduced. This
> > > patch reduces the average thermal pressure for a cpu from its maximum
> > > available capacity so that cpu_capacity reflects the actual
> > > available capacity.
> > > 
> > > Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> > > ---
> > >  kernel/sched/fair.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > > index 4f9c2cb..be3e802 100644
> > > --- a/kernel/sched/fair.c
> > > +++ b/kernel/sched/fair.c
> > > @@ -7727,6 +7727,7 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
> > >  
> > >  	used = READ_ONCE(rq->avg_rt.util_avg);
> > >  	used += READ_ONCE(rq->avg_dl.util_avg);
> > > +	used += READ_ONCE(rq->avg_thermal.load_avg);
> > 
> > Maybe a naive question - but can we add util_avg with load_avg without
> > a conversion? I thought the 2 signals have different properties.
> 
> Changelog of patch #1 explains, it's in that dense blob of text.
> 
> But yes, you're quite right that that wants a comment here.

Thanks for the pointer! A comment would be nice indeed.

To make sure I got this correctly - it's because avg_thermal.load_avg
represents delta_capacity which is already a 'converted' form of load. So this
makes avg_thermal.load_avg a util_avg really. Correct?

If I managed to get it right somehow. It'd be nice if we can do inverse
conversion on delta_capacity so that avg_thermal.{load_avg, util_avg} meaning
is consistent across the board. But I don't feel strongly about it if this gets
documented properly.

Thanks

--
Qais Yousef