On Fri, 03 Jul 2009, Pedro R wrote: > > Hi! > > I'll resume my problem: in CyclicTest I have an average of about 20-30us and peaks of 5000-6000us. These peaks are really annoying, since i'm using this system for firewire audio and each time there is a peak, an underrun in jackd causes a drop in sound. I have confirmed that these peaks are the direct cause of the underruns. > The peaks appear to occur randomly, most of the time in less than a minute of using CyclicTest and continue every minute or twice a minute (hard to say, since when CyclicTest hits a max value like 6000us, i'm not quick enough to read the actual peaks which achieve less than that - but the peaks continue). > > I left my system running the hwlat_detector module for 8 hours and all i got in the sample file was a bunch of 1's along with their timestamps, so the problem must not be the SMI. > > This problem also happens without the rt patch. I have tried using 2.6.26.2 (non-rt) kernel and I have the same problem. I also tried using 2.6.23-rt and 2.6.26-rt and it also happens. > two thoughts: - first it might be that you are runing a SCHED_FIFO task with a priority above the interrupt threads in which case you might be starving the data processing - second it might be a driver problem of the firewire driver you are using. so to detect case two with resonable likelyhood could you run cyclictest on an idle system for some time and on a loaded system not using the firewire ? but write the entire log into a file (sorry forgot which flag to cyclictest that was -v or -o I think) - look at the distribution of jitter not only the maxima. regarding the first case - check the priority of the SCHED_FIFO tasks in the system to make sure you are not simply starving the irq threads. hofrat -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
