linux-kernel - Re: [PATCH v2 00/19] Fixes for sched/numa

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Message-ID: <20180723152147.GE2494@hirez.programming.kicks-ass.net>
Date:   Mon, 23 Jul 2018 17:21:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 00/19]  Fixes for sched/numa_balancing

On Mon, Jul 23, 2018 at 08:09:55AM -0700, Srikar Dronamraju wrote:

> > >   sched/numa: Stop multiple tasks from moving to the cpu at the same time
> 
> This patch has go-ahead from Mel and Rik and no outstanding comments.

I left it out because it's part of the big xchg() mess.

In particular:

+       if (xchg(&rq->numa_migrate_on, 1))
+               return;
+
+       if (env->best_cpu != -1) {
+               rq = cpu_rq(env->best_cpu);
+               WRITE_ONCE(rq->numa_migrate_on, 0);
+       }

I'm again confused by clearing numa_migrate_on at this point..

> > >   sched/numa: Updation of scan period need not be in lock
> 
> I didnt see any comments for this apart from an ack from Rik.
> + It thought it was trivial and shouldnt have any side-effect.

Oh, my bad I actually have this one.