From: Mel Gorman <mgorman@techsingularity.net>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@surriel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/4] sched/numa: Do not move imbalanced load purely on the basis of an idle CPU
Date: Fri, 7 Sep 2018 15:28:46 +0100 [thread overview]
Message-ID: <20180907142846.GG1719@techsingularity.net> (raw)
In-Reply-To: <20180907134201.GC3995@linux.vnet.ibm.com>
On Fri, Sep 07, 2018 at 07:12:01PM +0530, Srikar Dronamraju wrote:
> > Yeah, I was afraid it would.. Srikar, can you also evaluate, I suspect
> > we'll have to pick one of these two patches.
>
> I can surely run some benchmarks between the two patches.
> However comparing Mel's patch with
> http://lkml.kernel.org/r/1533276841-16341-4-git-send-email-srikar@linux.vnet.ibm.com
>
> Mel's patch
>
> if (!cur) {
> - if (maymove || imp > env->best_imp)
> + if (maymove)
> goto assign;
> else
> http://lkml.kernel.org/r/1533276841-16341-4-git-send-email-srikar@linux.vnet.ibm.com
>
>
> if (!cur) {
> - if (maymove || imp > env->best_imp)
> + if (maymove && moveimp >= env->best_imp)
> goto assign;
> else
>
> In Mel's fix, if we already found a candidate task to swap and then encounter a
> idle cpu, we are going ahead and overwriting the swap candidate. There is
> always a chance that swap candidate is a better fit than moving to idle cpu.
>
There is a chance but to find out, the task has to be dequeued and requeued
on a maybe. An idle CPU is less disruptive and the only task affected is
migrating to the preferred node where, based on previous fault behaviour,
should have better locality. It's also a simplier patch but I'm going to
be biased towards my own patch, the tests will decide one way or the other.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2018-09-07 14:28 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 10:11 [PATCH 0/4] Follow-up fixes for v4.19-rc1 NUMA balancing Mel Gorman
2018-09-07 10:11 ` [PATCH 1/4] sched/numa: Remove redundant numa_stats nr_running field Mel Gorman
2018-09-07 10:11 ` [PATCH 2/4] sched/numa: Remove unused calculations in update_numa_stats Mel Gorman
2018-09-07 10:11 ` [PATCH 3/4] sched/numa: Stop comparing tasks for NUMA placement after selecting an idle core Mel Gorman
2018-09-07 13:05 ` Srikar Dronamraju
2018-09-07 14:20 ` Mel Gorman
2018-09-07 10:11 ` [PATCH 4/4] sched/numa: Do not move imbalanced load purely on the basis of an idle CPU Mel Gorman
2018-09-07 11:33 ` Peter Zijlstra
2018-09-07 12:37 ` Mel Gorman
2018-09-07 12:44 ` Peter Zijlstra
2018-09-07 13:42 ` Srikar Dronamraju
2018-09-07 14:28 ` Mel Gorman [this message]
2018-09-10 9:41 ` Mel Gorman
2018-09-12 6:54 ` Srikar Dronamraju
2018-09-12 9:36 ` Peter Zijlstra
2018-09-12 10:45 ` Srikar Dronamraju
2018-09-12 9:57 ` Ingo Molnar
2018-09-12 10:27 ` Srikar Dronamraju
2018-09-12 10:57 ` Mel Gorman
2018-09-12 10:52 ` Mel Gorman
2018-09-07 11:24 ` [PATCH 0/4] Follow-up fixes for v4.19-rc1 NUMA balancing Peter Zijlstra
2018-09-07 12:29 ` Mel Gorman
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