On Mon, Oct 18, 2004 at 05:44:52PM -0500, Zajac Adam-AAZ004 wrote: > It sounds like you're doing exactly what we've been trying to achieve. > We're trying to meet soft real-time deadlines that are in order of seconds > (2sec).
Hmm, 2s is a lot. You shouldn't have any problems with getting 2 second accuracy. > The only differences between our systems are: > - kernel 2.4.20 > - HZ = 100 > - Compact Flash And O(1) scheduler + SCHED_FIFO instead of round-robin (I don't like this scheduling policy :), SCHED_FIFO is true priority based scheduling. BTW, we have systems with CF card, writing to it doesn't seem to affect real-time threads either. > We tried to do a similar thing to the scenario you described where we were > running all other threads with SCHED_OTHER, and the thread with real-time > priority with RoundRobin scheduler policy. We keep experiencing the greatest > slips for such file system intensive operations like gzip and tar. > Also, for an experiment, we tried to turn disk caching off, which helped > meeting the deadlines a little but slowed down all file transfers > unacceptably. > To eliminate the question on the compact flash performance we tried using > NFS. Using NFS yielded similar results (missed deadlines) to performing the > transfers with the cflash card. > > Did you have to set anything special at your kernel config file (.config)? Nothing special I can think of. > Did you need to apply low-latency patch separately or the MV kernel you have > came pre-patched? I applied _all_ patches myself, although I used MV kernel as a reference in some cases, e.g. where rml PPC preempt patches were buggy. -- Eugene
