On Tue, Sep 5, 2023 at 7:10 AM Michal Koutný <mkoutny@xxxxxxxx> wrote: > > On Mon, Sep 04, 2023 at 05:41:10PM +0200, Michal Hocko <mhocko@xxxxxxxx> 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.
