On Thu, Aug 20, 2020 at 02:51:06PM +0200, Vincent Guittot wrote:
> On Thu, 20 Aug 2020 at 14:00, Jiang Biao <benbji...@gmail.com> wrote:
> >
> > From: Jiang Biao <benbji...@tencent.com>
> >
> > Vruntime compensation has been down in place_entity() to
> > boot the waking procedure for fair tasks. There is no need to
>
> s/boot/boost/ ?
>
> > do that for SCHED_IDLE task actually.
> >
> > Not compensating vruntime for SCHED_IDLE task could make
> > SCHED_IDLE task more harmless for normal tasks.
This is rather week. It would be much better if there's some actual data
to support this claim.
> > Signed-off-by: Jiang Biao <benbji...@tencent.com>
> > ---
> > kernel/sched/fair.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 1a68a0536add..adff77676a0a 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4115,7 +4115,7 @@ place_entity(struct cfs_rq *cfs_rq, struct
> > sched_entity *se, int initial)
> > vruntime += sched_vslice(cfs_rq, se);
> >
> > /* sleeps up to a single latency don't count. */
> > - if (!initial) {
> > + if (!initial && likely(!task_has_idle_policy(task_of(se)))) {
>
> What if se is not a task ?
Then we very much need it, because it might have fair tasks inside. I
suppose you could do something complicated with idle_h_nr_running, but
is all that really worth the effort?
> > unsigned long thresh = sysctl_sched_latency;
> >
> > /*
> > --
> > 2.21.0
> >
