Messages in this thread | | | Date | Tue, 8 Jul 2014 17:23:31 +0800 | From | "xiaofeng.yan" <> | Subject | Re: [PATCH] sched/deadline: overrun could happen in start_hrtick_dl |
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On 2014/7/8 16:53, xiaofeng.yan wrote:
Sorry, I send a old patch and send a new one later.
Thanks Yan > 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#trace-cmd record -e sched_switch & > PC#./schedtool -E -t 200000:500000 -e ./test > > Some of runtime and deadline run with millisecond level by > reading kernershark. Some pieces of trace.dat are as follows: > (remove some irrelevant information) > <idle>-0 157.603157: sched_switch: :R ==> 2481:4294967295: test > test-2481 157.603203: sched_switch: 2481:R ==> 0:120: swapper/2 > <idle>-0 157.605657: sched_switch: :R ==> 2481:4294967295: test > test-2481 157.608183: sched_switch: 2481:R ==> 2483:120: trace-cmd > trace-cmd-2483 157.609656: sched_switch:2483:R==>2481:4294967295: test > > We can get the runtime from the information at some point. > runtime = 157.605657 - 157.608183 > runtime = 0.002526(2.526ms) > The correct runtime should be less than or equal to 200us at some point. > > 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> > --- > 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..b71c229 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); > + delta = max_t(s64, 10000LL, delta); > + hrtick_start(rq, delta); > } > #endif >
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