Messages in this thread | | | Subject | Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4] | Date | Fri, 29 Oct 2004 16:51:55 -0400 | From | Paul Davis <> |
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[ I trimmed the CC: line because several people there are on jackit-devel. ]
>> compiles and boots fine. no observable change in xrun behaviour though. > >ok, so there's something else going on as well - or i missed an ioctl.
i really don't think the ioctl's are relevant.
consider what will happen if jackd does make a system call that causes a major delay (say, because of the BKL). we will get an xrun, yes, but this will cause jackd to stop the audio interface and restart. max_delay is not affected by this behaviour.
as far as i can tell, the number reported by max_delay entirely (or almost entirely) represents problems in kernel scheduling, specifically with a combination of:
a) handling the audio interface interrupt in time. b) marking the relevant jackd thread runnable c) context switching back to the relevant jackd thread
things that jackd does once its running do not, it appear to me, have any impact on max_delay, which is based on the simple observation:
"i was just woken, i expect to be awakened again in N usecs or less.
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