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. > > /* Check threshold */ > -- > 2.40.0.rc0.216.gc4246ad0f0-goog -- Michal Hocko SUSE Labs
