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SubjectRe: [PATCH v2] schied/fair: Skip calculating @contrib without load
On Fri, Dec 13, 2019 at 11:45:40AM +0800, Peng Wang wrote:
> diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
> index a96db50..4392953 100644
> --- a/kernel/sched/pelt.c
> +++ b/kernel/sched/pelt.c
> @@ -129,8 +129,9 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
> * Step 2
> */
> delta %= 1024;
> - contrib = __accumulate_pelt_segments(periods,
> - 1024 - sa->period_contrib, delta);
> + if (load)
> + contrib = __accumulate_pelt_segments(periods,
> + 1024 - sa->period_contrib, delta);
> }
> sa->period_contrib = delta;

I've made that:

--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -129,8 +129,20 @@ accumulate_sum(u64 delta, struct sched_a
* Step 2
*/
delta %= 1024;
- contrib = __accumulate_pelt_segments(periods,
- 1024 - sa->period_contrib, delta);
+ if (load) {
+ /*
+ * This relies on the:
+ *
+ * if (!load)
+ * runnable = running = 0;
+ *
+ * clause from ___update_load_sum(); this results in
+ * the below usage of @contrib to dissapear entirely,
+ * so no point in calculating it.
+ */
+ contrib = __accumulate_pelt_segments(periods,
+ 1024 - sa->period_contrib, delta);
+ }
}
sa->period_contrib = delta;

@@ -205,7 +217,9 @@ ___update_load_sum(u64 now, struct sched
* This means that weight will be 0 but not running for a sched_entity
* but also for a cfs_rq if the latter becomes idle. As an example,
* this happens during idle_balance() which calls
- * update_blocked_averages()
+ * update_blocked_averages().
+ *
+ * Also see the comment in accumulate_sum().
*/
if (!load)
runnable = running = 0;
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