On Wed, Mar 3, 2021 at 11:53 PM Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Wed, Mar 03, 2021 at 11:46:59AM +0800, Chengming Zhou wrote:
> > The commit 36b238d57172 ("psi: Optimize switching tasks inside shared
> > cgroups") only update cgroups whose state actually changes during a
> > task switch only in task preempt case, not in task sleep case.
> >
> > We actually don't need to clear and set TSK_ONCPU state for common cgroups
> > of next and prev task in sleep case, that can save many psi_group_change
> > especially when most activity comes from one leaf cgroup.
> >
> > sleep before:
> > psi_dequeue()
> > while ((group = iterate_groups(prev))) # all ancestors
> > psi_group_change(prev, .clear=TSK_RUNNING|TSK_ONCPU)
> > psi_task_switch()
> > while ((group = iterate_groups(next))) # all ancestors
> > psi_group_change(next, .set=TSK_ONCPU)
> >
> > sleep after:
> > psi_dequeue()
> > nop
> > psi_task_switch()
> > while ((group = iterate_groups(next))) # until (prev & next)
> > psi_group_change(next, .set=TSK_ONCPU)
> > while ((group = iterate_groups(prev))) # all ancestors
> > psi_group_change(prev, .clear=common?TSK_RUNNING:TSK_RUNNING|TSK_ONCPU)
> >
> > When a voluntary sleep switches to another task, we remove one call of
> > psi_group_change() for every common cgroup ancestor of the two tasks.
> >
> Co-developed-by: Muchun ?
Yes. Should Chengming send another version patch to add Co-developed-by tag?
> > Signed-off-by: Muchun Song <songmuc...@bytedance.com>
> > Signed-off-by: Chengming Zhou <zhouchengm...@bytedance.com>
