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

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Message-ID: <Y/TSAivRWwm2LaPh@hirez.programming.kicks-ass.net>
Date:   Tue, 21 Feb 2023 15:15:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.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, 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 :-)