sched: Fix sleep time double accounting in enqueue entity
authorAlex Shi <alex.shi@intel.com>
Thu, 20 Jun 2013 02:18:48 +0000 (10:18 +0800)
committerIngo Molnar <mingo@kernel.org>
Thu, 27 Jun 2013 08:07:32 +0000 (10:07 +0200)
commit282cf499f03ec1754b6c8c945c9674b02631fb0f
treea3f0c1ad7b760cf327ff566aa90efc41b71d3c4b
parenta75cdaa915e42ef0e6f38dc7f2a6a1deca91d648
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>
kernel/sched/fair.c