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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-01-15 14:53:39 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-01-15 15:12:19 +0100 |
commit | e17036dac189dd034c092a91df56aa740db7146d (patch) | |
tree | e4dc53a5ad8cccf71e611db3ee001a2e5a1e38f8 /kernel | |
parent | 6bc912b71b6f33b041cfde93ca3f019cbaa852bc (diff) | |
download | linux-e17036dac189dd034c092a91df56aa740db7146d.tar.gz |
sched: fix update_min_vruntime
Impact: fix SCHED_IDLE latency problems OK, so we have 1 running task A (which is obviously curr and the tree is equally obviously empty). 'A' nicely chugs along, doing its thing, carrying min_vruntime along as it goes. Then some whacko speed freak SCHED_IDLE task gets inserted due to SMP balancing, which is very likely far right, in that case update_curr update_min_vruntime cfs_rq->rb_leftmost := true (the crazy task sitting in a tree) vruntime = se->vruntime and voila, min_vruntime is waaay right of where it ought to be. OK, so why did I write it like that to begin with... Aah, yes. Say we've just dequeued current schedule deactivate_task(prev) dequeue_entity update_min_vruntime Then we'll set vruntime = cfs_rq->min_vruntime; we find !cfs_rq->curr, but do find someone in the tree. Then we _must_ do vruntime = se->vruntime, because vruntime = min_vruntime(vruntime := cfs_rq->min_vruntime, se->vruntime) will not advance vruntime, and cause lags the other way around (which we fixed with that initial patch: 1af5f730fc1bf7c62ec9fb2d307206e18bf40a69 (sched: more accurate min_vruntime accounting). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Mike Galbraith <efault@gmx.de> Acked-by: Mike Galbraith <efault@gmx.de> Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched_fair.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index cdebd8089cb0..16b419bb8b0a 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -283,7 +283,7 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq) struct sched_entity, run_node); - if (vruntime == cfs_rq->min_vruntime) + if (!cfs_rq->curr) vruntime = se->vruntime; else vruntime = min_vruntime(vruntime, se->vruntime); |