linux-kernel - [PATCH 1/7] sched: refactor tg_set_cfs

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Date:   Mon, 8 Apr 2019 14:45:33 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>
CC:     <mingo@...hat.com>, <peterz@...radead.org>,
        <vincent.guittot@...aro.org>, <tglx@...utronix.de>,
        <morten.rasmussen@....com>, <kernel-team@...com>,
        Song Liu <songliubraving@...com>
Subject: [PATCH 1/7] sched: refactor tg_set_cfs_bandwidth()

This patch factors tg_switch_cfs_runtime() out of tg_set_cfs_bandwidth(),
so that next patches can extend tg_switch_cfs_runtime() to support the new
target_idle_pct value.

This patch doesn't have any functionality changes.

Signed-off-by: Song Liu <songliubraving@...com>
---
 kernel/sched/core.c | 71 +++++++++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 32 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ead464a0f2e5..b8f220860dc7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6578,39 +6578,12 @@ const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
 
 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
 
-static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
+/* need get_online_cpus() and hold cfs_constraints_mutex */
+static void tg_switch_cfs_runtime(struct task_group *tg, u64 period, u64 quota)
 {
-	int i, ret = 0, runtime_enabled, runtime_was_enabled;
 	struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
-
-	if (tg == &root_task_group)
-		return -EINVAL;
-
-	/*
-	 * Ensure we have at some amount of bandwidth every period.  This is
-	 * to prevent reaching a state of large arrears when throttled via
-	 * entity_tick() resulting in prolonged exit starvation.
-	 */
-	if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
-		return -EINVAL;
-
-	/*
-	 * Likewise, bound things on the otherside by preventing insane quota
-	 * periods.  This also allows us to normalize in computing quota
-	 * feasibility.
-	 */
-	if (period > max_cfs_quota_period)
-		return -EINVAL;
-
-	/*
-	 * Prevent race between setting of cfs_rq->runtime_enabled and
-	 * unthrottle_offline_cfs_rqs().
-	 */
-	get_online_cpus();
-	mutex_lock(&cfs_constraints_mutex);
-	ret = __cfs_schedulable(tg, period, quota);
-	if (ret)
-		goto out_unlock;
+	int runtime_enabled, runtime_was_enabled;
+	int i;
 
 	runtime_enabled = quota != RUNTIME_INF;
 	runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
@@ -6647,7 +6620,41 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
 	}
 	if (runtime_was_enabled && !runtime_enabled)
 		cfs_bandwidth_usage_dec();
-out_unlock:
+}
+
+static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
+{
+	int ret = 0;
+
+	if (tg == &root_task_group)
+		return -EINVAL;
+
+	/*
+	 * Ensure we have at some amount of bandwidth every period.  This is
+	 * to prevent reaching a state of large arrears when throttled via
+	 * entity_tick() resulting in prolonged exit starvation.
+	 */
+	if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
+		return -EINVAL;
+
+	/*
+	 * Likewise, bound things on the otherside by preventing insane quota
+	 * periods.  This also allows us to normalize in computing quota
+	 * feasibility.
+	 */
+	if (period > max_cfs_quota_period)
+		return -EINVAL;
+
+	/*
+	 * Prevent race between setting of cfs_rq->runtime_enabled and
+	 * unthrottle_offline_cfs_rqs().
+	 */
+	get_online_cpus();
+	mutex_lock(&cfs_constraints_mutex);
+	ret = __cfs_schedulable(tg, period, quota);
+	if (!ret)
+		tg_switch_cfs_runtime(tg, period, quota);
+
 	mutex_unlock(&cfs_constraints_mutex);
 	put_online_cpus();
 
-- 
2.17.1