path: root/kernel
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authorAlex Shi <alex.shi@intel.com>2013-06-20 10:18:48 +0800
committerAlex Shi <alex.shi@linaro.org>2013-12-13 14:42:22 +0800
commitf0862cb749c537c32de82912d30110098ddc6cd6 (patch)
treef27ca6cd7145ebc734bd2e6a2d9dc1899e4c908c /kernel
parent7cf6a7300bb9a88f543061270419427395ab4d2f (diff)
sched: Fix sleep time double accounting in enqueue entity
The woken migrated task will __synchronize_entity_decay(se); in migrate_task_rq_fair, then it needs to set `se->avg.last_runnable_update -= (-se->avg.decay_count) << 20' before update_entity_load_avg, in order to avoid sleep time is updated twice for se.avg.load_avg_contrib in both __syncchronize and update_entity_load_avg. However if the sleeping task is woken up from the same cpu, it miss the last_runnable_update before update_entity_load_avg(se, 0, 1), then the sleep time was used twice in both functions. So we need to remove the double sleep time accounting. Paul also contributed some code comments in this commit. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-5-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a4a02740f0..b1e9def76b5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1714,7 +1714,13 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
wakeup = 0;
} else {
- __synchronize_entity_decay(se);
+ /*
+ * Task re-woke on same cpu (or else migrate_task_rq_fair()
+ * would have made count negative); we must be careful to avoid
+ * double-accounting blocked time after synchronizing decays.
+ */
+ se->avg.last_runnable_update += __synchronize_entity_decay(se)
+ << 20;
/* migrated tasks did not contribute to our blocked load */