lkml.org 
[lkml]   [2019]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] sched/fair: eliminate redundant code in sched_slice()
On 08/16/19 22:12, Peng Liu wrote:
> Since sched_slice() is used in high frequency,
> small change should also make sense.
>
> Signed-off-by: Peng Liu <iwtbavbm@gmail.com>
> ---
> kernel/sched/fair.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1054d2cf6aaa..6ae2a507aac0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -694,19 +694,16 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
> u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
>
> for_each_sched_entity(se) {
> - struct load_weight *load;
> struct load_weight lw;
>
> cfs_rq = cfs_rq_of(se);
> - load = &cfs_rq->load;
> + lw = cfs_rq->load;
>
> - if (unlikely(!se->on_rq)) {
> + if (unlikely(!se->on_rq))
> lw = cfs_rq->load;
>
> - update_load_add(&lw, se->load.weight);
> - load = &lw;
> - }
> - slice = __calc_delta(slice, se->load.weight, load);
> + update_load_add(&lw, se->load.weight);
> + slice = __calc_delta(slice, se->load.weight, &lw);

Unless I misread the diff, you changed the behavior.

update_load_add() is only called if (unlikely(!se->on_rq)), but with your
change it is called unconditionally. And lw is set twice.

I think what you intended is this?


diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bc9cfeaac8bd..6bbe17d5943f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -694,19 +694,15 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);

for_each_sched_entity(se) {
- struct load_weight *load;
struct load_weight lw;

cfs_rq = cfs_rq_of(se);
- load = &cfs_rq->load;
-
- if (unlikely(!se->on_rq)) {
- lw = cfs_rq->load;
+ lw = cfs_rq->load;

+ if (unlikely(!se->on_rq))
update_load_add(&lw, se->load.weight);
- load = &lw;
- }
- slice = __calc_delta(slice, se->load.weight, load);
+
+ slice = __calc_delta(slice, se->load.weight, &lw);
}
return slice;
}


Cheers

--
Qais Yousef

\
 
 \ /
  Last update: 2019-08-21 17:16    [W:0.193 / U:9.760 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site