From: Peter Zijlstra <peterz@infradead.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Ingo Molnar <mingo@kernel.org>, Phil Auld <pauld@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Quentin Perret <quentin.perret@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <Morten.Rasmussen@arm.com>,
Hillf Danton <hdanton@sina.com>, Parth Shah <parth@linux.ibm.com>,
Rik van Riel <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 v2
Date: Tue, 7 Jan 2020 13:28:09 +0100 [thread overview]
Message-ID: <20200107122809.GU2871@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200107112255.GV2827@hirez.programming.kicks-ass.net>
On Tue, Jan 07, 2020 at 12:22:55PM +0100, Peter Zijlstra wrote:
> On Tue, Jan 07, 2020 at 09:56:55AM +0000, Mel Gorman wrote:
> > + unsigned int imbalance_adj;
> > +
> > + /*
> > + * Calculate an acceptable degree of imbalance based
> > + * on imbalance_adj. However, do not allow a greater
> > + * imbalance than the child domains weight to avoid
> > + * a case where the allowed imbalance spans multiple
> > + * LLCs.
> > + */
>
> That comment is a wee misleading, @child is not an LLC per se. This
> could be the NUMA distance 2 domain, in which case @child is the NUMA
> distance 1 group.
>
> That said, even then it probably makes sense to ensure you don't idle a
> whole smaller distance group.
Hmm, one more thing. On AMD EPYC, which the multiple LLCs, you'll have
the single NODE domain in between, and that is not marked with SD_NUMA
(iirc).
So specifically the case you want to handle is not in fact handled. The
first SD_NUMA (distance-1) will have all NODE children, which on EPYC
are not LLCs.
next prev parent reply other threads:[~2020-01-07 12:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 8:42 [PATCH] sched, fair: Allow a small degree of load imbalance between SD_NUMA domains v2 Mel Gorman
2019-12-20 12:40 ` Valentin Schneider
2019-12-20 14:22 ` Mel Gorman
2019-12-20 15:32 ` Valentin Schneider
2019-12-21 11:25 ` Mel Gorman
2019-12-22 12:00 ` Srikar Dronamraju
2019-12-23 13:31 ` Vincent Guittot
2019-12-23 13:41 ` Vincent Guittot
2020-01-03 14:31 ` Mel Gorman
2020-01-06 13:55 ` Vincent Guittot
2020-01-06 14:52 ` Mel Gorman
2020-01-07 8:38 ` Vincent Guittot
2020-01-07 9:56 ` Mel Gorman
2020-01-07 11:17 ` Vincent Guittot
2020-01-07 11:56 ` Mel Gorman
2020-01-07 16:00 ` Vincent Guittot
2020-01-07 20:24 ` Mel Gorman
2020-01-08 8:25 ` Vincent Guittot
2020-01-08 8:49 ` Mel Gorman
2020-01-08 13:18 ` Peter Zijlstra
2020-01-08 14:03 ` Mel Gorman
2020-01-08 16:46 ` Vincent Guittot
2020-01-08 18:03 ` Mel Gorman
2020-01-07 11:22 ` Peter Zijlstra
2020-01-07 11:42 ` Mel Gorman
2020-01-07 12:29 ` Peter Zijlstra
2020-01-07 12:28 ` Peter Zijlstra [this message]
2020-01-07 19:26 ` Phil Auld
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