linux-kernel - [RFC patch 3/4] sched/cfs_rq: change atomic64_t removed_load to atomic_long

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Message-Id: <1370590169-24804-4-git-send-email-alex.shi@intel.com>
Date:	Fri,  7 Jun 2013 15:29:28 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, morten.rasmussen@....com
Cc:	vincent.guittot@...aro.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
	alex.shi@...el.com, mgorman@...e.de, riel@...hat.com,
	wangyun@...ux.vnet.ibm.com, Jason Low <jason.low2@...com>
Subject: [RFC patch 3/4] sched/cfs_rq: change atomic64_t removed_load to atomic_long_t

Like as runnable_load_avg, blocked_load_avg variable, long type is
enough for removed_load in 64 bit or 32 bit machine.

Then we avoid the expensive atomic64 operations on 32 bit machine.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 kernel/sched/fair.c  | 10 ++++++----
 kernel/sched/sched.h |  3 ++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 30fb7dc..9cc4211 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1517,8 +1517,9 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
 	if (!decays && !force_update)
 		return;
 
-	if (atomic64_read(&cfs_rq->removed_load)) {
-		u64 removed_load = atomic64_xchg(&cfs_rq->removed_load, 0);
+	if (atomic_long_read(&cfs_rq->removed_load)) {
+		unsigned long removed_load;
+		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
 		subtract_blocked_load_contrib(cfs_rq, removed_load);
 	}
 
@@ -3479,7 +3480,8 @@ migrate_task_rq_fair(struct task_struct *p, int next_cpu)
 	 */
 	if (se->avg.decay_count) {
 		se->avg.decay_count = -__synchronize_entity_decay(se);
-		atomic64_add(se->avg.load_avg_contrib, &cfs_rq->removed_load);
+		atomic_long_add(se->avg.load_avg_contrib,
+						&cfs_rq->removed_load);
 	}
 }
 #endif /* CONFIG_SMP */
@@ -5944,7 +5946,7 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
 #endif
 #if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
 	atomic64_set(&cfs_rq->decay_counter, 1);
-	atomic64_set(&cfs_rq->removed_load, 0);
+	atomic_long_set(&cfs_rq->removed_load, 0);
 #endif
 }
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1bfa91a..874731f 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -278,8 +278,9 @@ struct cfs_rq {
 	 * the FAIR_GROUP_SCHED case).
 	 */
 	unsigned long runnable_load_avg, blocked_load_avg;
-	atomic64_t decay_counter, removed_load;
+	atomic64_t decay_counter;
 	u64 last_decay;
+	atomic_long_t removed_load;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	/* Required to track per-cpu representation of a task_group */
-- 
1.7.12

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