From: Mel Gorman <mgorman@techsingularity.net>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Phil Auld <pauld@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
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 load imbalance between low utilisation SD_NUMA domains v4
Date: Fri, 17 Jan 2020 14:15:03 +0000 [thread overview]
Message-ID: <20200117141503.GQ3466@techsingularity.net> (raw)
In-Reply-To: <CAKfTPtBznUt20QFzeQBPELcmN6+F=BOx09oSqVMzSGvXF5ByHg@mail.gmail.com>
On Fri, Jan 17, 2020 at 02:08:13PM +0100, Vincent Guittot wrote:
> > > This patch allows a fixed degree of imbalance of two tasks to exist
> > > between NUMA domains regardless of utilisation levels. In many cases,
> > > this prevents communicating tasks being pulled apart. It was evaluated
> > > whether the imbalance should be scaled to the domain size. However, no
> > > additional benefit was measured across a range of workloads and machines
> > > and scaling adds the risk that lower domains have to be rebalanced. While
> > > this could change again in the future, such a change should specify the
> > > use case and benefit.
> > >
> >
> > Any thoughts on whether this is ok for tip or are there suggestions on
> > an alternative approach?
>
> I have just finished to run some tests on my system with your patch
> and I haven't seen any noticeable any changes so far which was a bit
> expected. The tests that I usually run, use more than 4 tasks on my 2
> nodes system;
This is indeed expected. With more active tasks, normal load balancing
applies.
> the only exception is perf sched pipe and the results
> for this test stays the same with and without your patch.
I never saw much difference with perf sched pipe either. It was
generally within the noise.
> I'm curious
> if this impacts Phil's tests which run LU.c benchmark with some
> burning cpu tasks
I didn't see any problem with LU.c whether parallelised by openMPI or
openMP but an independent check would be nice.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2020-01-17 14:15 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 10:13 [PATCH] sched, fair: Allow a small load imbalance between low utilisation SD_NUMA domains v4 Mel Gorman
2020-01-16 16:35 ` Mel Gorman
2020-01-17 13:08 ` Vincent Guittot
2020-01-17 14:15 ` Mel Gorman [this message]
2020-01-17 14:32 ` Phil Auld
2020-01-17 14:23 ` Phil Auld
2020-01-17 14:37 ` Valentin Schneider
2020-01-17 13:16 ` Vincent Guittot
2020-01-17 14:26 ` Mel Gorman
2020-01-17 14:29 ` Vincent Guittot
2020-01-17 15:09 ` Vincent Guittot
2020-01-17 15:11 ` Peter Zijlstra
2020-01-17 15:21 ` Phil Auld
2020-01-17 17:56 ` Srikar Dronamraju
2020-01-17 21:58 ` Mel Gorman
2020-01-20 8:09 ` Srikar Dronamraju
2020-01-20 8:33 ` Mel Gorman
2020-01-20 17:27 ` Srikar Dronamraju
2020-01-20 18:21 ` Mel Gorman
2020-01-21 8:55 ` Srikar Dronamraju
2020-01-21 9:11 ` Mel Gorman
2020-01-21 10:42 ` Peter Zijlstra
2020-01-21 9:59 ` Srikar Dronamraju
2020-01-29 11:32 ` [tip: sched/core] sched/fair: Allow a small load imbalance between low utilisation SD_NUMA domains tip-bot2 for Mel Gorman
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