linux-kernel - [PATCH 8/8] sched/fair: delete superfluous SKIP_AGE

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Date:   Sat,  9 Jul 2022 23:13:53 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: [PATCH 8/8] sched/fair: delete superfluous SKIP_AGE_LOAD

All three attach_entity_cfs_rq() types:

1. task migrate CPU
2. task migrate cgroup
3. task switched to fair

have its sched_avg last_update_time reset to 0 when
attach_entity_cfs_rq() -> update_load_avg(), so it makes
no difference whether SKIP_AGE_LOAD is set or not.

This patch delete the superfluous SKIP_AGE_LOAD, and the unused
feature ATTACH_AGE_LOAD together.

Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 kernel/sched/fair.c     | 18 ++++++------------
 kernel/sched/features.h |  1 -
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b0bde895ba96..b91643a2143e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3956,9 +3956,8 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
  * Optional action to be done while updating the load average
  */
 #define UPDATE_TG	0x1
-#define SKIP_AGE_LOAD	0x2
-#define DO_ATTACH	0x4
-#define DO_DETACH	0x8
+#define DO_ATTACH	0x2
+#define DO_DETACH	0x4
 
 /* Update task and its cfs_rq load average */
 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
@@ -3970,7 +3969,7 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
 	 * Track task load average for carrying it to new CPU after migrated, and
 	 * track group sched_entity load average for task_h_load calc in migration
 	 */
-	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
+	if (se->avg.last_update_time)
 		__update_load_avg_se(now, cfs_rq, se);
 
 	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
@@ -4253,7 +4252,6 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 }
 
 #define UPDATE_TG	0x0
-#define SKIP_AGE_LOAD	0x0
 #define DO_ATTACH	0x0
 #define DO_DETACH	0x0
 
@@ -11484,9 +11482,7 @@ static void detach_entity_cfs_rq(struct sched_entity *se)
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
 	/* Catch up with the cfs_rq and remove our load when we leave */
-	update_load_avg(cfs_rq, se, 0);
-	detach_entity_load_avg(cfs_rq, se);
-	update_tg_load_avg(cfs_rq);
+	update_load_avg(cfs_rq, se, UPDATE_TG | DO_DETACH);
 	propagate_entity_cfs_rq(se);
 }
 
@@ -11494,10 +11490,8 @@ static void attach_entity_cfs_rq(struct sched_entity *se)
 {
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
-	/* Synchronize entity with its cfs_rq */
-	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
-	attach_entity_load_avg(cfs_rq, se);
-	update_tg_load_avg(cfs_rq);
+	/* Synchronize entity with its cfs_rq and attach our load */
+	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
 	propagate_entity_cfs_rq(se);
 }
 
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index ee7f23c76bd3..fb92431d496f 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -85,7 +85,6 @@ SCHED_FEAT(RT_PUSH_IPI, true)
 
 SCHED_FEAT(RT_RUNTIME_SHARE, false)
 SCHED_FEAT(LB_MIN, false)
-SCHED_FEAT(ATTACH_AGE_LOAD, true)
 
 SCHED_FEAT(WA_IDLE, true)
 SCHED_FEAT(WA_WEIGHT, true)
-- 
2.36.1