Messages in this thread | | | Subject | Re: [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion | From | "brookxu.cn" <> | Date | Fri, 24 Sep 2021 23:21:19 +0800 |
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Thanks for your time.
On 2021/9/24 10:01 PM, Michal Hocko wrote: > 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?
Just a optimization point discovered during the diagnosis, no behavior change.
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