On Tue 14-09-21 16:23:16, Michal Koutny wrote: > On Tue, Sep 14, 2021 at 09:13:48AM +0200, Michal Hocko <mhocko@xxxxxxxx> wrote: > > " > > This object can consume up to 2 pages, syscall is sleeping one, > > size and duration can be controlled by user, and this allocation > > can be repeated by many thread at the same time. > > " > > > > It sounds like a problem, except it is not because? A worst case > > scenario evaluation would be beneficial for example > > AFAICS, the offending allocation is in place only during the duration of > the syscall. So it's basically O(#tasks). > Considering at least 2 pages for task_struct + 2 pages for kernel stack, > back of the envelope calculation gives me the footprint amplification is > <1.5. > The factor would IMO be interesting if it was >> 2 (from the PoV of > excessive (ab)use, fine-grained accounting seems to be currently > unfeasible due to performance impact). Yes this sounds exactly like something I would appreciate in the changelog. With that or similar feel free to add Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks a lot Michal for this clarification! > The commit message can be more explicit about this but to the patch > Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx> -- Michal Hocko SUSE Labs
