From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH 2/3] sched/numa: Allow a floating imbalance between NUMA nodes
Date: Tue, 17 Nov 2020 14:43:52 +0000 [thread overview]
Message-ID: <20201117144352.GZ3371@techsingularity.net> (raw)
In-Reply-To: <20201117141603.GM3121392@hirez.programming.kicks-ass.net>
On Tue, Nov 17, 2020 at 03:16:03PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 17, 2020 at 01:42:21PM +0000, Mel Gorman wrote:
> > This patch revisits the possibility that NUMA nodes can be imbalanced
> > until 25% of the CPUs are occupied. The reasoning behind 25% is somewhat
> > superficial -- it's half the cores when HT is enabled. At higher
> > utilisations, balancing should continue as normal and keep things even
> > until scheduler domains are fully busy or over utilised.
>
> Do we want to make that shift depend on the actual SMT factor?
I considered it but decided against it. I wanted the balance point to
be somewhere below SMT because select_idle_sibling tries to avoid SMT
sharing so I didn't want a point where SMT sharing caused more problems
than memory locality. However, I worried that picking a different imbalance
point depending on SMT would be surprising to some.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2020-11-17 14:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 13:42 [RFC PATCH 0/3] Revisit NUMA imbalance tolerance and fork balancing Mel Gorman
2020-11-17 13:42 ` [PATCH 1/3] sched/numa: Rename nr_running and break out the magic number Mel Gorman
2020-11-17 13:42 ` [PATCH 2/3] sched/numa: Allow a floating imbalance between NUMA nodes Mel Gorman
2020-11-17 14:16 ` Peter Zijlstra
2020-11-17 14:43 ` Mel Gorman [this message]
2020-11-17 14:24 ` Vincent Guittot
2020-11-17 14:44 ` Mel Gorman
2020-11-17 13:42 ` [PATCH 3/3] sched/numa: Limit the amount of imbalance that can exist at fork time Mel Gorman
2020-11-17 14:18 ` Peter Zijlstra
2020-11-17 14:31 ` Vincent Guittot
2020-11-17 15:17 ` Mel Gorman
2020-11-17 15:53 ` Vincent Guittot
2020-11-17 17:28 ` Mel Gorman
2020-11-18 16:06 ` Vincent Guittot
2020-11-18 16:50 ` Mel Gorman
2020-11-22 15:04 ` [sched/numa] e7f28850ea: unixbench.score 1.5% improvement kernel test robot
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