lkml.org 
[lkml]   [2021]   [Mar]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 9/9] sched,fair: Alternative sched_slice()
On Fri, Mar 26, 2021 at 04:37:03PM +0100, Vincent Guittot wrote:
> On Fri, 26 Mar 2021 at 11:43, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > The current sched_slice() seems to have issues; there's two possible
> > things that could be improved:
> >
> > - the 'nr_running' used for __sched_period() is daft when cgroups are
> > considered. Using the RQ wide h_nr_running seems like a much more
> > consistent number.
> >
> > - (esp) cgroups can slice it real fine, which makes for easy
> > over-scheduling, ensure min_gran is what the name says.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> > kernel/sched/fair.c | 15 ++++++++++++++-
> > kernel/sched/features.h | 3 +++
> > 2 files changed, 17 insertions(+), 1 deletion(-)
> >
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -680,7 +680,16 @@ static u64 __sched_period(unsigned long
> > */
> > static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
> > {
> > - u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
> > + unsigned int nr_running = cfs_rq->nr_running;
> > + u64 slice;
> > +
> > + if (sched_feat(ALT_PERIOD))
> > + nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
> > +
> > + slice = __sched_period(nr_running + !se->on_rq);
> > +
> > + if (sched_feat(BASE_SLICE))
> > + slice -= sysctl_sched_min_granularity;
> >
> > for_each_sched_entity(se) {
> > struct load_weight *load;
> > @@ -697,6 +706,10 @@ static u64 sched_slice(struct cfs_rq *cf
> > }
> > slice = __calc_delta(slice, se->load.weight, load);
> > }
> > +
> > + if (sched_feat(BASE_SLICE))
> > + slice += sysctl_sched_min_granularity;
>
> Why not only doing a max of slice and sysctl_sched_min_granularity
> instead of scaling only the part above sysctl_sched_min_granularity ?
>
> With your change, cases where the slices would have been in a good
> range already, will be modified as well

Can do I suppose. Not sure how I ended up with this.

\
 
 \ /
  Last update: 2021-03-26 19:33    [W:0.118 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site