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

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Date:   Thu, 15 Apr 2021 09:17:37 -0400
From:   Waiman Long <llong@...hat.com>
To:     Masayoshi Mizuma <msys.mizuma@...il.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>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>
Subject: Re: [PATCH v3 0/5] mm/memcg: Reduce kmemcache memory accounting
 overhead

On 4/14/21 11:26 PM, Masayoshi Mizuma wrote:
>
> Hi Longman,
>
> Thank you for your patches.
> I rerun the benchmark with your patches, it seems that the reduction
> is small... The total duration of sendto() and recvfrom() system call
> during the benchmark are as follows.
>
> - sendto
>    - v5.8 vanilla:                      2576.056 msec (100%)
>    - v5.12-rc7 vanilla:                 2988.911 msec (116%)
>    - v5.12-rc7 with your patches (1-5): 2984.307 msec (115%)
>
> - recvfrom
>    - v5.8 vanilla:                      2113.156 msec (100%)
>    - v5.12-rc7 vanilla:                 2305.810 msec (109%)
>    - v5.12-rc7 with your patches (1-5): 2287.351 msec (108%)
>
> kmem_cache_alloc()/kmem_cache_free() are called around 1,400,000 times during
> the benchmark. I ran a loop in a kernel module as following. The duration
> is reduced by your patches actually.
>
>    ---
>    dummy_cache = KMEM_CACHE(dummy, SLAB_ACCOUNT);
>    for (i = 0; i < 1400000; i++) {
> 	p = kmem_cache_alloc(dummy_cache, GFP_KERNEL);
> 	kmem_cache_free(dummy_cache, p);
>    }
>    ---
>
> - v5.12-rc7 vanilla:                 110 msec (100%)
> - v5.12-rc7 with your patches (1-5):  85 msec (77%)
>
> It seems that the reduction is small for the benchmark though...
> Anyway, I can see your patches reduce the overhead.
> Please feel free to add:
>
> 	Tested-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
>
> Thanks!
> Masa
>
Thanks for the testing.

I was focusing on your kernel module benchmark in testing my patch. I 
will try out your pgbench benchmark to see if there can be other tuning 
that can be done.

BTW, how many numa nodes does your test machine? I did my testing with a 
2-socket system. The vmstat caching part may be less effective on 
systems with more numa nodes. I will try to find a larger 4-socket 
systems for testing.

Cheers,
Longman