Re: [PATCH v2 1/1] cgroup: make per-cgroup pressure stall tracking configurable

[Suren Baghdasaryan]

On Tue, May 18, 2021 at 11:55 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> On Tue, May 18, 2021 at 11:52 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >
> > On Mon, May 17, 2021 at 07:02:00PM -0700, Suren Baghdasaryan wrote:
> >
> > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> > > index cc25a3cff41f..4b8e72640ac9 100644
> > > --- a/kernel/sched/psi.c
> > > +++ b/kernel/sched/psi.c
> > > @@ -148,6 +148,7 @@
> > >  static int psi_bug __read_mostly;
> > >
> > >  DEFINE_STATIC_KEY_FALSE(psi_disabled);
> > > +DEFINE_STATIC_KEY_FALSE(psi_cgroups_disabled);
> >
> > I'm thinking the whole thing will be easier/clearer when you make this:
> >
> > DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled);
> >
>
> Sounds good. Will respin another version. Thanks for reviewing!

v3 is posted at https://lore.kernel.org/patchwork/patch/1435705

>
>
> > >
> > >  #ifdef CONFIG_PSI_DEFAULT_DISABLED
> > >  static bool psi_enable;
> > > @@ -211,6 +212,9 @@ void __init psi_init(void)
> > >               return;
> > >       }
> > >
> > > +     if (!cgroup_psi_enabled())
> > > +             static_branch_enable(&psi_cgroups_disabled);
> >
> >         if (!cgroup_psi_enabled())
> >                 static_branch_disable(&psi_cgroups_enabled);
> >
> > > +
> > >       psi_period = jiffies_to_nsecs(PSI_FREQ);
> > >       group_init(&psi_system);
> > >  }
> > > @@ -744,23 +748,23 @@ static void psi_group_change(struct psi_group *group, int cpu,
> > >
> > >  static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
> > >  {
> > > +     if (*iter == &psi_system)
> > > +             return NULL;
> > > +
> > >  #ifdef CONFIG_CGROUPS
> > > +     if (!static_branch_likely(&psi_cgroups_disabled)) {
> >
> >         if (static_branch_likely(&psi_cgroups_enabled)) {
> >
> > > +             struct cgroup *cgroup = NULL;
> > >
> > > +             if (!*iter)
> > > +                     cgroup = task->cgroups->dfl_cgrp;
> > > +             else
> > > +                     cgroup = cgroup_parent(*iter);
> > >
> > > +             if (cgroup && cgroup_parent(cgroup)) {
> > > +                     *iter = cgroup;
> > > +                     return cgroup_psi(cgroup);
> > > +             }
> > >       }
> > >  #endif
> > >       *iter = &psi_system;
> > >       return &psi_system;
> >
> > But yes, very nice.
> >
> > --
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> >