linux-kernel - Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO

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Date:   Fri, 7 Sep 2018 10:54:04 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Daniel Drake <drake@...lessm.com>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Christopher Lameter <cl@...ux.com>,
        Peter Enderborg <peter.enderborg@...y.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Mike Galbraith <efault@....de>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and
 IO

On Fri, Sep 07, 2018 at 12:24:58PM +0200, Peter Zijlstra wrote:
> On Tue, Aug 28, 2018 at 01:22:57PM -0400, Johannes Weiner wrote:
> > +static void psi_clock(struct work_struct *work)
> > +{
> > +	struct delayed_work *dwork;
> > +	struct psi_group *group;
> > +	bool nonidle;
> > +
> > +	dwork = to_delayed_work(work);
> > +	group = container_of(dwork, struct psi_group, clock_work);
> > +
> > +	/*
> > +	 * If there is task activity, periodically fold the per-cpu
> > +	 * times and feed samples into the running averages. If things
> > +	 * are idle and there is no data to process, stop the clock.
> > +	 * Once restarted, we'll catch up the running averages in one
> > +	 * go - see calc_avgs() and missed_periods.
> > +	 */
> > +
> > +	nonidle = update_stats(group);
> > +
> > +	if (nonidle) {
> > +		unsigned long delay = 0;
> > +		u64 now;
> > +
> > +		now = sched_clock();
> > +		if (group->next_update > now)
> > +			delay = nsecs_to_jiffies(group->next_update - now) + 1;
> > +		schedule_delayed_work(dwork, delay);
> > +	}
> > +}
> 
> Just a little nit; I would expect a function called *clock() to return a
> time.

Fair enough, let's rename this. How about this on top?

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 92489e66840b..0f07749b60a4 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -154,7 +154,7 @@ static struct psi_group psi_system = {
 	.pcpu = &system_group_pcpu,
 };
 
-static void psi_clock(struct work_struct *work);
+static void psi_update_work(struct work_struct *work);
 
 static void group_init(struct psi_group *group)
 {
@@ -163,7 +163,7 @@ static void group_init(struct psi_group *group)
 	for_each_possible_cpu(cpu)
 		seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq);
 	group->next_update = sched_clock() + psi_period;
-	INIT_DELAYED_WORK(&group->clock_work, psi_clock);
+	INIT_DELAYED_WORK(&group->clock_work, psi_update_work);
 	mutex_init(&group->stat_lock);
 }
 
@@ -347,7 +347,7 @@ static bool update_stats(struct psi_group *group)
 	return nonidle_total;
 }
 
-static void psi_clock(struct work_struct *work)
+static void psi_update_work(struct work_struct *work)
 {
 	struct delayed_work *dwork;
 	struct psi_group *group;