Messages in this thread | | | Date | Tue, 8 Jul 2014 09:49:43 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/rt: overrun could happen in start_hrtick_dl |
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On Tue, Jul 08, 2014 at 10:51:02AM +0800, xiaofeng.yan wrote: > On 2014/7/8 10:40, Li Zefan wrote: > >On 2014/7/8 9:10, xiaofeng.yan wrote: > >>On 2014/7/7 16:41, Peter Zijlstra wrote: > >>>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 ? > >>yes, If HRTICK is close , then all of runtime and deadline will be wrong. > >I think what peter meant is, do you use HRTICK in products or > >just use it for testing/experiment? > > > Thanks for your timely comments. In fact, We use HRTICK feature in product. > We need microsecond level > precision.
Ah, thanks. Be advised that currently HRTICK is rather expensive. The cost is twofold: 1) doing all the kernel side hrtimer things and 2) programming clock hardware.
Of course, if that's what you need, you're willing to pay the price.
I'll see if I can put making it less expensive slightly higher on the (endless) todo list. [unhandled content-type:application/pgp-signature] | |