Messages in this thread | | | From | Yosry Ahmed <> | Date | Tue, 5 Sep 2023 08:54:46 -0700 | Subject | Re: [PATCH v4 3/4] mm: memcg: let non-unified root stats flushes help unified flushes |
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On Tue, Sep 5, 2023 at 7:10 AM Michal Koutný <mkoutny@suse.com> wrote: > > On Mon, Sep 04, 2023 at 05:41:10PM +0200, Michal Hocko <mhocko@suse.com> wrote: > > So it also creates an undocumented but userspace visible behavior. > > Something that userspace might start depending on, right? > > Yes but - > - depending on undocumented behavior is a mistake, > - breaking the dependency would manifest (in the case I imagine) as a > performance regression (and if there are some users, the future can > allow them configuring periodic kernel flush to compensate for that).
I think I am missing something. This change basically makes userspace readers (for the root memcg) help out unified flushers, which are in-kernel readers (e.g. reclaim) -- not the other way around.
How would that create a userspace visible behavior that a dependency can be formed on? Users expecting reclaim to be faster right after reading root stats? I would guess that would be too flaky to cause a behavior that people can depend on tbh.
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