linux-kernel - Re: [PATCH v3 0/5] mm/memcg: Reduce kmemcache memory accounting overhead

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Date:   Thu, 15 Apr 2021 18:10:35 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <guro@...com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Chris Down <chris@...isdown.name>,
        Yafang Shao <laoar.shao@...il.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Masayoshi Mizuma <msys.mizuma@...il.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>
Subject: Re: [PATCH v3 0/5] mm/memcg: Reduce kmemcache memory accounting
 overhead

On Tue, Apr 13, 2021 at 09:20:22PM -0400, Waiman Long wrote:
> With memory accounting disable, the run time was 2.848s. With memory
> accounting enabled, the run times with the application of various
> patches in the patchset were:
> 
>   Applied patches   Run time   Accounting overhead   Overhead %age
>   ---------------   --------   -------------------   -------------
>        None          10.800s         7.952s              100.0%
>         1-2           9.140s         6.292s               79.1%
>         1-3           7.641s         4.793s               60.3%
>         1-5           6.801s         3.953s               49.7%

I think this is a misleading way to report the overhead.  I would have said:

			10.800s		7.952s		279.2%
			 9.140s		6.292s		220.9%
			 7.641s		4.793s		168.3%
			 6.801s		3.953s		138.8%