On 2017-02-05 19:11:01 [+0200], Ran Shalit wrote: > Hello, Hi, > We made some testing on out cpu, installed with 4.1.15-rt17 kernel, > and we observed significant difference in latency between posic to > non-posix cyclictest benchmark. > > with non posix we reach max ~50usec > while with posix we reach max ~170usec > > On checking the exaples in cyclic test wiki, it seems that the > difference should not be that big : > https://rt.wiki.kernel.org/index.php/Cyclictest > > What is the reason for such difference in behaviour ? > Does it mean we better use non-posix timer in application ? As written in the other thread (regarding posix-timer): I tested today v4.9-RT and didn't notice such high spikes between clock_nanosleep and the posix timer. You have the consider that the wakeup happens from ktimersoftirq so you have one additional context switch here. I general the clock_nansleep interface should be preferred if possible to avoid that ctx switch. Sebastian -- 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
