linux-kernel - Re: [PATCH v10 5/9] sched/fair: Take into account latency priority at wakeup

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Message-ID: <CAKfTPtAHuVFx=5w0p5DBShx42eEPCPXJ+DLc3z3_3yFv9jJWeA@mail.gmail.com>
Date:   Tue, 21 Feb 2023 15:25:36 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, juri.lelli@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org, parth@...ux.ibm.com,
        cgroups@...r.kernel.org, qyousef@...alina.io,
        chris.hyser@...cle.com, patrick.bellasi@...bug.net,
        David.Laight@...lab.com, pjt@...gle.com, pavel@....cz,
        tj@...nel.org, qperret@...gle.com, tim.c.chen@...ux.intel.com,
        joshdon@...gle.com, timj@....org, kprateek.nayak@....com,
        yu.c.chen@...el.com, youssefesmat@...omium.org,
        joel@...lfernandes.org
Subject: Re: [PATCH v10 5/9] sched/fair: Take into account latency priority at wakeup

On Tue, 21 Feb 2023 at 15:15, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Feb 21, 2023 at 01:52:58PM +0100, Peter Zijlstra wrote:
> > On Fri, Jan 13, 2023 at 03:12:30PM +0100, Vincent Guittot wrote:
> >
> > > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > > index 6c61bde49152..38decae3e156 100644
> > > --- a/include/linux/sched.h
> > > +++ b/include/linux/sched.h
> > > @@ -568,6 +568,8 @@ struct sched_entity {
> > >     /* cached value of my_q->h_nr_running */
> > >     unsigned long                   runnable_weight;
> > >  #endif
> > > +   /* preemption offset in ns */
> > > +   long                            latency_offset;
> >
> > I wonder about the type here; does it make sense to have it depend on
> > the bitness; that is if s32 is big enough on 32bit then surely it is so
> > too on 64bit, and if not, then it should be unconditionally s64.
> >
>
> The cgroup patch has this as 'int'. I'm thinking we ought to be
> consistent :-)

Yes, good point