On Mon, 2011-02-14 at 15:08 -0800, Peter LaDow wrote:
> Note sure how that is possible. This is related to my earlier posting
> about timing jitter. Our code is basically this:
>
Where is the semicolon ending the for loop?
> while(1)
> {
> t1 = clock_gettime()
> for(i=0; i < 10000; i++)
> t2 = clock_gettime()
>
> diff = t2 - 1
> }
>
> This task is pending on nothing. Unless clock_gettime() causes some
> sort of priority inversion, I don't see the problem. We see
> significant jitter on the for-loop when there are a significant number
> of other kernel timers. Now, as we understand it, the hrtimers run in
> the softirq. But if the softirq is priority 50, and this for-loop is
> priority 99, it shouldn't be affected by the softirq thread.
>
> Pete
>
> On Mon, Feb 14, 2011 at 3:04 PM, Sven-Thorsten Dietrich
> <thebigcorporation@xxxxxxxxx> wrote:
> > On Mon, 2011-02-14 at 14:31 -0800, Peter LaDow wrote:
> >> How is the scheduling of the hrtimers softirq thread handled?
> >>
> >> When querying the RT priority of the hrtimer softirq, I get a priority
> >> of 50. But when running a priority 99 thread, we still seem to be
> >> getting interrupted. Shouldn't the hrtimer softirq be put off until
> >> the CPU is idle or a lower priority task is running?
> >
> > Does your prio 99 thread perhaps encounter a prio inversion dependency
> > on one of the softriq threads?
> >
> >>
> >> Thanks,
> >> Pete
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> >
> >
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