From: Michal Hocko <mhocko@suse.com>
To: brookxu <brookxu.cn@gmail.com>
Cc: hannes@cmpxchg.org, vdavydov.dev@gmail.com,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org
Subject: Re: [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion
Date: Fri, 24 Sep 2021 16:01:51 +0200 [thread overview]
Message-ID: <YU3aT7i2vBNxewam@dhcp22.suse.cz> (raw)
In-Reply-To: <03145735-7764-4cd4-e15b-60402f4b447e@gmail.com>
On Fri 24-09-21 21:02:52, brookxu wrote:
> 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@tencent.com>
> >>
> >> 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.
OK, so why do we want to optimize this code?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-09-24 14:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-24 6:46 [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion brookxu
2021-09-24 6:46 ` [PATCH 2/2] mem_cgroup: introduce foreign_writeback_in_process() function brookxu
2021-09-24 9:34 ` [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion Michal Hocko
2021-09-24 13:02 ` brookxu
2021-09-24 14:01 ` Michal Hocko [this message]
2021-09-24 15:21 ` brookxu.cn
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