Hi > after some chatting with Nicholas and being sure that I didn't do anything > totally stupid I would like to provide my current kernel config and a trace > generated by "cyclictest ... -b500". > > kernel config -> https://www.dropbox.com/s/zsud0b77xoosjm1/config > trace -> > https://www.dropbox.com/s/5uf58oqo0qwcn4x/trace-cyclictest-2508us.txt > > I still get max latencies of about 4000us on this TI AM335x system running > 3.12.6-rt9 with timers-do-not-raise-softirq-unconditionally.patch reverse > applied. > > sched_rt_runtime_us and sched_rt_period_us are identical. The system is idle > during the test. Rootfilesystem comes via NFS. > > root@generic-armv7a:~# cat /proc/sys/kernel/sched_rt_runtime_us > 1000000 > root@generic-armv7a:~# cat /proc/sys/kernel/sched_rt_period_us > 1000000 > > root@generic-armv7a:~# uname -a > Linux generic-armv7a 3.12.6-rt9-dirty #3 SMP PREEMPT RT Sat Jan 4 23:01:19 > CET 2014 armv7l GNU/Linux > > root@generic-armv7a:~# ~/cyclictest -p99 -m -n -i200 -h400 -q -l100000 -b > 500 # /dev/cpu_dma_latency set to 0us > INFO: debugfs mountpoint: /sys/kernel/debug/tracing/ > could not set ftrace_enabled to 0 > could not set tracing_max_latency to 0 > # Histogram > ... > # Total: 000018604 > # Min Latencies: 00024 > # Avg Latencies: 00158 > # Max Latencies: 02508 Wohaa, thats bad for a latency patched kernel. Have you disabled powermanagement? I have an older rt patched kernel and it was not too good. If i remember correctly it was between 100-200µs latency. But thats far better than this. You could also load the system with hackbench, if its the idle pm than latency would get better. Best regards Tim -- 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
