On Fri, 2017-02-10 at 20:07 +0100, Sebastian Andrzej Siewior wrote:

On 2017-02-08 18:41:25 [+0000], Patel, Vedang wrote:

quoted

Hi, 

Hi,

quoted

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

Thanks,
Vedang

quoted

Thanks,
Vedang Patel
Software Engineer
Intel Corporation

Sebastian