Messages in this thread Patch in this message | | | Subject | Re: problem with "sched: revert back to per-rq vruntime"? | From | Mike Galbraith <> | Date | Wed, 31 Dec 2008 17:26:13 +0100 |
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On Tue, 2008-12-30 at 13:37 -0600, Jayson King wrote: > Here's some times using bash, for example. Let me know if there are some > other tests I can do. >
> [jayson@atlas tmp]$ time bash -i -c 'exit' > exit > > real 0m0.753s > user 0m0.011s > sys 0m0.011s
Yeah, it's b0rked. The problem is that we call sched_slice() before the new task's load weight has been added to the runqueue.
Normally this doesn't cause horrible problems, but when there is a +nice hog on the runqueue, the lighter the hog, and/or heavier the victim...
[ 160.489402] bash:5858 vslice: 3840000000 weight: 1024 rq_weight: 15 inv_weight: 268435456
...the closer the victim's vruntime gets to the middle of next week.
Not-signed-off diag hack.
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 5ad4440..3254213 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -449,13 +449,34 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) } /* + * A freshly forked task's load weight has not yet been added to the runqueue, + * so we can't call calc_delta_weight() and get sane results. Therefore, we roll + * our own so place_entity() can place this task in the right spot. The runqueue + * weight and nr_running will be updated when the task is enqueued. + */ +static u64 sched_initial_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) +{ + u64 slice = __sched_period(cfs_rq->nr_running + 1); + + for_each_sched_entity(se) { + struct load_weight lw = cfs_rq->load; + + lw.weight += se->load.weight; + lw.inv_weight = 0; + slice = calc_delta_mine(slice, se->load.weight, &lw); + } + + return slice; +} + +/* * We calculate the vruntime slice of a to be inserted task * * vs = s/w */ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) { - return calc_delta_fair(sched_slice(cfs_rq, se), se); + return calc_delta_fair(sched_initial_slice(cfs_rq, se), se); } /*
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