linux-kernel - Re: [mm/migrate] 9eeb73028c: stress-ng.memhotplug.ops_per

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Date:   Mon, 06 Sep 2021 09:53:39 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     kernel test robot <oliver.sang@...el.com>,
        Rui Zhang <rui.zhang@...el.com>, Chen Yu <yu.c.chen@...el.com>,
        Len Brown <len.brown@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        0day robot <lkp@...el.com>, Yang Shi <shy828301@...il.com>,
        Zi Yan <ziy@...dia.com>, Michal Hocko <mhocko@...e.com>,
        Wei Xu <weixugc@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Rientjes <rientjes@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Greg Thelen <gthelen@...gle.com>,
        Keith Busch <kbusch@...nel.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        LKML <linux-kernel@...r.kernel.org>, <lkp@...ts.01.org>,
        <feng.tang@...el.com>, <zhengjun.xing@...ux.intel.com>,
        <dave.hansen@...ux.intel.com>, <linux-mm@...ck.org>,
        <mm-commits@...r.kernel.org>, <torvalds@...ux-foundation.org>
Subject: Re: [mm/migrate]  9eeb73028c:  stress-ng.memhotplug.ops_per_sec
 -53.8% regression

kernel test robot <oliver.sang@...el.com> writes:

> Greeting,
>
> FYI, we noticed a -53.8% regression of stress-ng.memhotplug.ops_per_sec due to commit:
>
>
> commit: 9eeb73028cfb54eb06efe87c50cc014d3f1ff43e ("[patch 174/212] mm/migrate: update node demotion order on hotplug events")
> url: https://github.com/0day-ci/linux/commits/Andrew-Morton/ia64-fix-typo-in-a-comment/20210903-065028
>
>
> in testcase: stress-ng
> on test machine: 96 threads 2 sockets Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 192G memory
> with following parameters:
>
> 	nr_threads: 10%
> 	disk: 1HDD
> 	testtime: 60s
> 	fs: ext4
> 	class: os
> 	test: memhotplug
> 	cpufreq_governor: performance
> 	ucode: 0x5003006
>

Because we added some operations during online/offline CPU, it's
expected that the performance of online/offline CPU will decrease.  In
most cases, the performance of CPU hotplug isn't a big problem.  But
then I remembers that the performance of the CPU hotplug may influence
suspend/resume performance :-(

It appears that it is easy and reasonable to enclose the added
operations inside #ifdef CONFIG_NUMA.  Is this sufficient to restore the
performance of suspend/resume?

Best Regards,
Huang, Ying