sched: Add a timer to handle CFS bandwidth refresh

This patch adds a per-task_group timer which handles the refresh of the global
CFS bandwidth pool.

Since the RT pool is using a similar timer there's some small refactoring to
share this support.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.277271273@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 37 insertions, 3 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 9502aa899f73..af73a8a85eef 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1284,9 +1284,16 @@ static void assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
         raw_spin_lock(&cfs_b->lock);
         if (cfs_b->quota == RUNTIME_INF)
                 amount = min_amount;
-        else if (cfs_b->runtime > 0) {
-                amount = min(cfs_b->runtime, min_amount);
-                cfs_b->runtime -= amount;
+        else {
+                /* ensure bandwidth timer remains active under consumption */
+                if (!cfs_b->timer_active)
+                        __start_cfs_bandwidth(cfs_b);
+
+                if (cfs_b->runtime > 0) {
+                        amount = min(cfs_b->runtime, min_amount);
+                        cfs_b->runtime -= amount;
+                        cfs_b->idle = 0;
+                }
         }
         raw_spin_unlock(&cfs_b->lock);
 
@@ -1315,6 +1322,33 @@ static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
         __account_cfs_rq_runtime(cfs_rq, delta_exec);
 }
 
+/*
+ * Responsible for refilling a task_group's bandwidth and unthrottling its
+ * cfs_rqs as appropriate. If there has been no activity within the last
+ * period the timer is deactivated until scheduling resumes; cfs_b->idle is
+ * used to track this state.
+ */
+static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
+{
+        int idle = 1;
+
+        raw_spin_lock(&cfs_b->lock);
+        /* no need to continue the timer with no bandwidth constraint */
+        if (cfs_b->quota == RUNTIME_INF)
+                goto out_unlock;
+
+        idle = cfs_b->idle;
+        cfs_b->runtime = cfs_b->quota;
+
+        /* mark as potentially idle for the upcoming period */
+        cfs_b->idle = 1;
+out_unlock:
+        if (idle)
+                cfs_b->timer_active = 0;
+        raw_spin_unlock(&cfs_b->lock);
+
+        return idle;
+}
 #else
 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
                                      unsigned long delta_exec) {}