Re: [Xenomai] Xenomai-forge: thread using 100% cpu load

[Philippe Gerum <rpm@xenomai.org>]

On 03/02/2013 12:13 PM, Ronny Meeus wrote:

> An update on the investigation:
> I was able to make this issue disappear by changing the timeout value
> of the smallest timers we use.
> We use a couple of timers with a timeout of 25ms. By enlarging these
> to 25sec and the problem is gone.
>
> Yesterday I was also able to see (using the"strace" tool) the process
> executing constantly "clone" system calls.
> Note that the process we use is large (2Gb) and uses an mlockall call.
>
> In http://stackoverflow.com/questions/4263958/some-information-on-timer-helper-thread-of-librt-so-1/4935895#4935895
> I see that a new thread is created when the timer_create is called for
> the first time. This thread stays alive until the program exits and is
> used to process the timer expiries.

Looking at the code, glibc 2.9 not only forks one helper thread once, 
but also creates a dedicated short-lived thread for running the user 
handler at each timer expiration. This implementation is still current 
with 2.15. Which makes quite too many clones out there for my taste.

-- 
Philippe.