On Fri, 2006-06-23 at 12:12 +0200, Pieter Palmers wrote:
> Lee Revell wrote:
>
> >On Fri, 2006-06-23 at 09:44 +0930, Jonathan Woithe wrote:
> >
> >
> >>Despite what the log says, this was running a 2.0 GHz "Dothan"
> >>Centrino CPU. Kernel was 2.6.16-rt25, distro was Slackware 10.2. Both
> >>the stress tester and the monitor were run with RT privilege access.
> >>The firewire interface used has a TI OHCI chipset.
> >>
> >>I apologise that the run was particularly short and that therefore the
> >>statistics aren't particularly good, but it does seem to confirm the
> >>observations you made on your machine. The large latencies only occur
> >>when the stress tester is running.
> >>
> >>
> >
> >What if you run the latency tester at RT priority 99? Testing at 80 is
> >not particularly useful.
> >
> >
> Why not?
>
> If the 1394 test user thread has a lower priority, and the ohci1394 irq
> priority is also lower, there is no reason for the latency tester to be
> preempted by them.
>
Because as you stated below the system timer runs at a higher priority
by default. I wanted to rule out preemption by the system timer thread.
> >If anything else is running at 99, what happens if you lower those other
> >processes to 98?
> >
> >
> I'll have to recheck, but if I remember correcly I have done this
> experiment. The only thing at 99 is the system timer. I tried giving it
> a lower priority than the latency test thread, which didn't change anything.
>
OK thanks, that answers my question.
> Pieter
>
Received on Sat Jun 24 04:15:07 2006
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