From mboxrd@z Thu Jan  1 00:00:00 1970
From: brookxu <brookxu.cn-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 1/2] mem_cgroup: optimize the atomic count of
 wb_completion
Date: Fri, 24 Sep 2021 21:02:52 +0800
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To: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

Thanks for your time.

Michal Hocko wrote on 2021/9/24 17:34:
> On Fri 24-09-21 14:46:22, brookxu wrote:
>> From: Chunguang Xu <brookxu-1Nz4purKYjRBDgjK7y7TUQ@public.gmane.org>
>>
>> In order to track inflight foreign writeback, we init
>> wb_completion.cnt to 1. For normal writeback, this cause
>> wb_wait_for_completion() to perform meaningless atomic
>> operations. Since foreign writebacks rarely occur in most
>> scenarios, we can init wb_completion.cnt to 0 and set
>> frn.done.cnt to 1. In this way we can avoid unnecessary
>> atomic operations.
> 
> Does this lead to any measurable differences?

I created multiple cgroups that performed IO on multiple disks, 
then flushed the cache with sync command, and no measurable
differences have been observed so far.

>