Hi! On 13:02 Thu 16 Oct , Valdis.Kletnieks@vt.edu wrote:
On Thu, 16 Oct 2014 14:09:05 +0200, "Nev Ikte" said:
I've tried to reproduce it with a single client and basically, if ep_poll() is able to find an event or the timeout is 0, the latency is down to 5usec, otherwise if it enters the waitqueue the latency goes up to 10-25usec, which impact the application performance.
Is it possible that what you're actually measuring here is your CPU's latency coming out of a sleep state if every task is in a wait queue?
I have seen wakeup latencies of ~100usec on some systems. You may want to disable sleep states and see of performance gets better. Take a look at: Documentation/power/pm_qos_interface.txt Also, you probably want disable frequency scaling: /sys/devices/system/cpu/cpu.../cpufreq/scaling_governor should return "performance" for every cpu. You can change it with eche "performance" > /sys/... -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com