On Mon, Feb 13, 2017 at 8:48 PM, Patel, Vedang <vedang.patel@xxxxxxxxx> wrote: > On Fri, 2017-02-10 at 20:07 +0100, Sebastian Andrzej Siewior wrote: >> On 2017-02-08 18:41:25 [+0000], Patel, Vedang wrote: >> > >> > Hi, >> Hi, >> >> > >> > The results for the POSIX timers were not as I expected. The >> > latency >> > for real-time kernel (v4.9.4-rt2) was worse compared to the >> > mainline >> > kernel (v4.9.4). In almost all the cases, the latency is almost >> > doubled >> > with the max value reaching about 10 times when performing the >> > tests >> > under load. >> Is it also the case if you boost the priority of ktimersoftd/X >> threads? >> For clock_nanosleep, the wake-ups happen directly from hard-timer >> interrupt. For the posix-timer we have to delay those to the >> ktimersoftd >> thread which runs usually RT prio 1. >> > I am getting very similar results even if I change the priority of > ktimersoftd to 99. Are there any recent rt patches which might have > changed the behaviour of POSIX timers? > > Also, are POSIX timers really suited for "real-time" applications?I > believe a similar question was raised by Ran Shalit a few days back: > http://www.spinics.net/lists/linux-rt-users/msg16249.html > Right. I did testing of recent kernels 4.1.15, with Atom , and the non-posix timers jitter was obviously better compared to non-posix (42usec vs 180us), On trying 4.4.x kernel I seen very strange behavior for both timers (maybe I applied the patch wrongly or needed to disable some features in config?) , So I decided eventually to use the 4.1.15 with non-posix timers only with our Atom board. I hope that's a good decision. > Thanks, > Vedang >> > >> > Thanks, >> > Vedang Patel >> > Software Engineer >> > Intel Corporation >> 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
