From: Mel Gorman <mgorman@suse.de>
To: Barry Song <song.bao.hua@hisilicon.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
bsegall@google.com, linux-kernel@vger.kernel.org,
linuxarm@huawei.com, Mel Gorman <mgorman@techsingularity.net>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Valentin Schneider <valentin.schneider@arm.com>,
Phil Auld <pauld@redhat.com>, Hillf Danton <hdanton@sina.com>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] sched/fair: use dst group while checking imbalance for NUMA balancer
Date: Mon, 7 Sep 2020 10:27:17 +0100 [thread overview]
Message-ID: <20200907092717.GD3117@suse.de> (raw)
In-Reply-To: <20200907072708.8664-1-song.bao.hua@hisilicon.com>
On Mon, Sep 07, 2020 at 07:27:08PM +1200, Barry Song wrote:
> Something is wrong. In find_busiest_group(), we are checking if src has
> higher load, however, in task_numa_find_cpu(), we are checking if dst
> will have higher load after balancing. It seems it is not sensible to
> check src.
> It maybe cause wrong imbalance value, for example, if
> dst_running = env->dst_stats.nr_running + 1 results in 3 or above, and
> src_running = env->src_stats.nr_running - 1 results in 1;
> The current code is thinking imbalance as 0 since src_running is smaller
> than 2.
> This is inconsistent with load balancer.
>
It checks the conditions if the move was to happen. Have you evaluated
this for a NUMA balancing load and confirmed it a) balances properly and
b) does not increase the scan rate trying to "fix" the problem?
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2020-09-07 9:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-07 7:27 Barry Song
2020-09-07 9:27 ` Mel Gorman [this message]
2020-09-07 9:44 ` Song Bao Hua (Barry Song)
2020-09-07 10:44 ` Mel Gorman
2020-09-07 12:31 ` Srikar Dronamraju
[not found] ` <20200908010717.12436-1-hdanton@sina.com>
2020-09-10 21:50 ` Jirka Hladky
2020-09-21 11:02 ` Mel Gorman
2020-09-21 16:02 ` Jirka Hladky
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