Messages in this thread Patch in this message | | | Date | Mon, 7 Jul 2014 10:41:50 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/rt: overrun could happen in start_hrtick_dl |
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On Fri, Jul 04, 2014 at 12:02:21PM +0000, xiaofeng.yan wrote: > It could be wrong for the precision of runtime and deadline > when the precision is within microsecond level. For example: > Task runtime deadline period > P1 200us 500us 500us > > This case need enbale HRTICK feature by the next command > PC#echo "HRTICK" > /sys/kernel/debug/sched_features > PC#./schedtool -E -t 200000:500000 -e ./test& > PC#trace-cmd record -e sched_switch
Are you actually using HRTICK ?
> Some of runtime and deadline run with millisecond level by > reading kernershark. > The problem is caused by a conditional judgment "delta > 10000". > Because no hrtimer start up to control the runtime when runtime is less than 10us. > So the process will continue to run until tick-period coming. > For fixing this problem, Let delta is equal to 10us when it is less than 10us. > So the hrtimer will start up to control the end of process. > > Signed-off-by: xiaofeng.yan <xiaofeng.yan@huawei.com>
Always when sending patches for deadline, also CC Juri.
> --- > kernel/sched/deadline.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index fc4f98b1..dfefa82 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -997,10 +997,8 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, > #ifdef CONFIG_SCHED_HRTICK > static void start_hrtick_dl(struct rq *rq, struct task_struct *p) > { > - s64 delta = p->dl.dl_runtime - p->dl.runtime; > - > - if (delta > 10000) > - hrtick_start(rq, p->dl.runtime); > + s64 delta = p->dl.runtime > 10000 ? p->dl.runtime : 10000; > + hrtick_start(rq, delta);
Yeah, that looks funny. And seeing how the only other user does something similar:
hrtick_start_fair() delta = max(10000ULL, delta) hrtick_start(rq, delta)
Does it make sense to move this max() into hrtick_start()?
Also; and I don't think you mentioned that but did fix, the argument to hrtick_start() is wrong, it should be the delta, not the absolute timeout. [unhandled content-type:application/pgp-signature] | |