linux-kernel - Re: [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task cookie on fork

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Date:   Thu, 5 Nov 2020 09:49:19 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     chris hyser <chris.hyser@...cle.com>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        torvalds@...ux-foundation.org, fweisbec@...il.com,
        keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>, vineeth@...byteword.org,
        Chen Yu <yu.c.chen@...el.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Agata Gruza <agata.gruza@...el.com>,
        Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>,
        graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com,
        pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com,
        benbjiang@...cent.com,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        James.Bottomley@...senpartnership.com, OWeisse@...ch.edu,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Tim Chen <tim.c.chen@...el.com>
Subject: Re: [PATCH v8 -tip 17/26] sched: Split the cookie and setup per-task
 cookie on fork

On Wed, Nov 04, 2020 at 05:30:24PM -0500, chris hyser wrote:
[..]
> +		wr.cookies[0] = cookie;
> > +	} else
> > +	/*
> > +	 * 		t1		joining		t2
> > +	 * CASE 1:
> > +	 * before	0				0
> > +	 * after	new cookie			new cookie
> > +	 *
> > +	 * CASE 2:
> > +	 * before	X (non-zero)			0
> > +	 * after	0				0
> > +	 *
> > +	 * CASE 3:
> > +	 * before	0				X (non-zero)
> > +	 * after	X				X
> > +	 *
> > +	 * CASE 4:
> > +	 * before	Y (non-zero)			X (non-zero)
> > +	 * after	X				X
> > +	 */
> > +	if (!t1->core_task_cookie && !t2->core_task_cookie) {
> > +		/* CASE 1. */
> > +		cookie = sched_core_alloc_task_cookie();
> > +		if (!cookie)
> > +			goto out_unlock;
> > +
> > +		/* Add another reference for the other task. */
> > +		if (!sched_core_get_task_cookie(cookie)) {
> > +			return -EINVAL;
> 
> should be:              ret = -EINVAL;

Fixed now, thanks.

thanks,

 - Joel


> 
> > +			goto out_unlock;
> > +		}
> > +
> > +		wr.tasks[0] = t1;
> > +		wr.tasks[1] = t2;
> > +		wr.cookies[0] = wr.cookies[1] = cookie;
> > +
> > +	} else if (t1->core_task_cookie && !t2->core_task_cookie) {
> > +		/* CASE 2. */
> > +		sched_core_put_task_cookie(t1->core_task_cookie);
> > +		sched_core_put_after_stopper = true;
> > +
> > +		wr.tasks[0] = t1; /* Reset cookie for t1. */
> > +
> > +	} else if (!t1->core_task_cookie && t2->core_task_cookie) {
> > +		/* CASE 3. */
> > +		if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> > +			ret = -EINVAL;
> > +			goto out_unlock;
> > +		}
> > +
> > +		wr.tasks[0] = t1;
> > +		wr.cookies[0] = t2->core_task_cookie;
> > +
> > +	} else {
> > +		/* CASE 4. */
> > +		if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> > +			ret = -EINVAL;
> > +			goto out_unlock;
> > +		}
> > +		sched_core_put_task_cookie(t1->core_task_cookie);
> > +		sched_core_put_after_stopper = true;
> > +
> > +		wr.tasks[0] = t1;
> > +		wr.cookies[0] = t2->core_task_cookie;
> > +	}
> > +
> > +	stop_machine(sched_core_task_join_stopper, (void *)&wr, NULL);
> > +
> > +	if (sched_core_put_after_stopper)
> > +		sched_core_put();
> > +
> > +	ret = 0;
> > +out_unlock:
> > +	mutex_unlock(&sched_core_mutex);
> > +	return ret;
> > +}
> > +
> > +/* CGroup interface */
> >   static u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
> >   {
> >   	struct task_group *tg = css_tg(css);
> > @@ -9207,18 +9435,9 @@ static int __sched_write_tag(void *data)
> >   	 * when we set cgroup tag to 0 when the loop is done below.
> >   	 */
> >   	while ((p = css_task_iter_next(&it))) {
> > -		p->core_cookie = !!val ? (unsigned long)tg : 0UL;
> > -
> > -		if (sched_core_enqueued(p)) {
> > -			sched_core_dequeue(task_rq(p), p);
> > -			if (!p->core_cookie)
> > -				continue;
> > -		}
> > -
> > -		if (sched_core_enabled(task_rq(p)) &&
> > -		    p->core_cookie && task_on_rq_queued(p))
> > -			sched_core_enqueue(task_rq(p), p);
> > +		unsigned long cookie = !!val ? (unsigned long)tg : 0UL;
> > +		sched_core_tag_requeue(p, cookie, true /* group */);
> >   	}
> >   	css_task_iter_end(&it);
> > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> > index c8fee8d9dfd4..88bf45267672 100644
> > --- a/kernel/sched/debug.c
> > +++ b/kernel/sched/debug.c
> > @@ -1024,6 +1024,10 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
> >   		__PS("clock-delta", t1-t0);
> >   	}
> > +#ifdef CONFIG_SCHED_CORE
> > +	__PS("core_cookie", p->core_cookie);
> > +#endif
> > +
> >   	sched_show_numa(p, m);
> >   }
> > 
> 
> -chrish