From: Vincent Guittot <vincent.guittot@xxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== commit 9390675af0835ae1d654d33bfcf16096028550ad upstream. This reverts commit 282cf499f03ec1754b6c8c945c9674b02631fb0f. With the current implementation, the load average statistics of a sched entity change according to other activity on the CPU even if this activity is done between the running window of the sched entity and have no influence on the running duration of the task. When a task wakes up on the same CPU, we currently update last_runnable_update with the return of __synchronize_entity_decay without updating the runnable_avg_sum and runnable_avg_period accordingly. In fact, we have to sync the load_contrib of the se with the rq's blocked_load_contrib before removing it from the latter (with __synchronize_entity_decay) but we must keep last_runnable_update unchanged for updating runnable_avg_sum/period during the next update_entity_load_avg. Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Reviewed-by: Ben Segall <bsegall@xxxxxxxxxx> Cc: pjt@xxxxxxxxxx Cc: alex.shi@xxxxxxxxxx Link: http://lkml.kernel.org/r/1390376734-6800-1-git-send-email-vincent.guittot@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- kernel/sched/fair.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 790e2fc808da..25658d2c68d0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1579,13 +1579,7 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, } wakeup = 0; } else { - /* - * 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; + __synchronize_entity_decay(se); } /* migrated tasks did not contribute to our blocked load */ -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html