linux-kernel - Re: [RFC PATCH] sched/numa: fix bug in update_task_scan

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Message-ID: <20200814131554.GH3510@suse.de>
Date:   Fri, 14 Aug 2020 14:15:54 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     ????????? <tianchen.dingtianc@...baba-inc.com>
Cc:     'Ingo Molnar' <mingo@...hat.com>,
        'Peter Zijlstra' <peterz@...radead.org>,
        'Juri Lelli' <juri.lelli@...hat.com>,
        'Vincent Guittot' <vincent.guittot@...aro.org>,
        'Dietmar Eggemann' <dietmar.eggemann@....com>,
        'Steven Rostedt' <rostedt@...dmis.org>,
        'Ben Segall' <bsegall@...gle.com>,
        'linux-kernel' <linux-kernel@...r.kernel.org>,
        '??????' <yun.wang@...ux.alibaba.com>
Subject: Re: [RFC PATCH] sched/numa: fix bug in update_task_scan_period

On Wed, Aug 12, 2020 at 11:51:54AM +0800, ????????? wrote:
> OK. Thanks for your advice and I'll use label instead.
> In the case of migration failures, if there are still new failures after
> clearing (meaning the node is still overloaded), the scanning period would
> be doubled, just like not using this patch. However, if the failures do not
> increase again, then the scanning period should be adjusted according to the
> following rules (i.e., ps and lr ratio). I believe this is the original
> design idea, right?
> 

The original idea was to simply throttle scanning if the faults were
useless. Your patch is probably correct but I would still like to see
some evidence of the user-visible impact. What tests have you conducted
to make sure it behaves better (or is at least neutral in most cases)?

-- 
Mel Gorman
SUSE Labs