On Fri, Dec 05, 2008 at 08:11:36AM -0800, Pete wrote: > So even if the kernel is not a RT kernel, processes can run with real > time priority? How is this so? From what ive read about the RT kernel > it sounds like the kernel has to cooperate with the processes running > on the system to allow a process to awaken (on an interrupt for instance). > Otherwise the kernel will be stuck in some non interruptable state for > some time, blocking the interrupt from being serviced - is that wrong? > > If Jack has a way to grab higher priority through some other mechanisim, > could I build this into arecord I wonder. I have of course tried nicing > the process to very unnice. nice values are irrelevant to processes with rtprio. Any rtprio process will have priority over any process with just a nice value. jackd -R defaults to rtprio 10 (in a range of 0-99). You can raise that by specifying the value on the command line eg. jackd -R -P80 which would increase it to 80 (usually unnecessary and possibly inadvisable). You can look at what's running with rtprio on your system with ps, eg.: ps -Leo pid,cmd,rtprio rtprio makes use of SCHED_FIFO or SCHED_RR (as opposed to SCHED_NORMAL). These are static soft realtime scheduling policies provided by the standard kernel. The -rt kernels attempt to get closer to hard realtime. Don't confuse the two. On the current kernels, a non-root user has to belong to a realtime scheduling group (eg. the audio group) and the kernel config needs to have CONFIG_RT_GROUP_SCHED=y to allow rtprio to be used. The relevant configuration must also be present in /etc/security/limits.conf. There are plenty of articles on the web describing how to set up limits.conf. John _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
