On Thu, Mar 2, 2023 at 5:58 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Wed 01-03-23 11:34:03, Suren Baghdasaryan wrote: > > Current 500ms min window size for psi triggers limits polling interval > > to 50ms to prevent polling threads from using too much cpu bandwidth by > > polling too frequently. However the number of cgroups with triggers is > > unlimited, so this protection can be defeated by creating multiple > > cgroups with psi triggers (triggers in each cgroup are served by a single > > "psimon" kernel thread). > > Instead of limiting min polling period, which also limits the latency of > > psi events, it's better to limit psi trigger creation to authorized users > > only, like we do for system-wide psi triggers (/proc/pressure/* files can > > be written only by processes with CAP_SYS_RESOURCE capability). This also > > makes access rules for cgroup psi files consistent with system-wide ones. > > Add a CAP_SYS_RESOURCE capability check for cgroup psi file writers and > > remove the psi window min size limitation. > > > > Suggested-by: Sudarshan Rajagopalan <quic_sudaraja@xxxxxxxxxxx> > > Link: https://lore.kernel.org/all/cover.1676067791.git.quic_sudaraja@xxxxxxxxxxx/ > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > > with this to fix > [...] > > @@ -1278,8 +1277,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, > > if (state >= PSI_NONIDLE) > > return ERR_PTR(-EINVAL); > > > > - if (window_us < WINDOW_MIN_US || > > - window_us > WINDOW_MAX_US) > > + if (window_us <= 0 || window_us > WINDOW_MAX_US) > > return ERR_PTR(-EINVAL); > > window_us is u32 sp the check for <= 0 doesn't make any sense. Completely missed that. Will change to == 0 and post the new version. window_us is later multiplied by NSEC_PER_USEC and then divided by UPDATES_PER_WINDOW(10), so even the smallest value of 1 still results in a positive poll_min_period. I think we should be fine with that check. Thanks! > > > > > /* Check threshold */ > > -- > > 2.40.0.rc0.216.gc4246ad0f0-goog > > -- > Michal Hocko > SUSE Labs
