From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
pauld@redhat.com, valentin.schneider@arm.com,
quentin.perret@arm.com, dietmar.eggemann@arm.com,
Morten.Rasmussen@arm.com, hdanton@sina.com, parth@linux.ibm.com,
riel@surriel.com, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched, fair: Allow a small degree of load imbalance between SD_NUMA domains
Date: Fri, 20 Dec 2019 18:30:56 +0530 [thread overview]
Message-ID: <20191220130056.GA13192@linux.vnet.ibm.com> (raw)
In-Reply-To: <20191219144539.GA19614@linaro.org>
* Vincent Guittot <vincent.guittot@linaro.org> [2019-12-19 15:45:39]:
> Hi Mel,
>
> Thanks for looking at this NUMA locality vs spreading tasks point.
>
>
> Shouldn't you consider the number of busiest->idle_cpus instead of the busiest->sum_nr_running ?
> and you could simplify by
>
>
> if ((env->sd->flags & SD_NUMA) &&
> ((100 * busiest->group_weight) <= (env->sd->imbalance_pct * (busiest->idle_cpus << 1)))) {
> env->imbalance = 0;
> return;
> }
Are idle_cpus and sum_nr_running good enough metrics to look at a NUMA
level? We could have asymmetric NUMA topology where one DIE/MC/groups may
have more cores than the other. In such a case looking at idle_cpus (or
sum_nr_running) of the group may not always lead us to the right load
balancing solution.
--
Thanks and Regards
Srikar Dronamraju
prev parent reply other threads:[~2019-12-20 13:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-18 15:44 [PATCH] sched, fair: Allow a small degree of load imbalance between SD_NUMA domains Mel Gorman
2019-12-18 18:50 ` Valentin Schneider
2019-12-18 22:50 ` Mel Gorman
2019-12-19 11:56 ` Valentin Schneider
2019-12-19 10:02 ` Peter Zijlstra
2019-12-19 11:46 ` Valentin Schneider
2019-12-19 14:23 ` Valentin Schneider
2019-12-19 15:23 ` Mel Gorman
2019-12-18 18:54 ` Valentin Schneider
2019-12-19 2:58 ` Rik van Riel
2019-12-19 8:41 ` Mel Gorman
2019-12-19 10:04 ` Peter Zijlstra
2019-12-19 14:45 ` Vincent Guittot
2019-12-19 15:16 ` Valentin Schneider
2019-12-19 15:18 ` Mel Gorman
2019-12-19 15:41 ` Vincent Guittot
2019-12-19 15:58 ` Mel Gorman
2019-12-20 13:00 ` Srikar Dronamraju [this message]
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