Re: random performance of sem_post function

[Carlos O'Donell <carlos at systemhalted dot org>]

On 01/05/2013 08:43 AM, Maury, Olivier wrote:
> I'm using RHEL 6.2 64 bits on a regular intel nehalem server. I also
> have that behavior on Centos 5.3 with the same kind of HW. I'll try
> oprofile, I never used it so I hope it doesn't require root
> privileges as I don't have any. I tried intel Vtune and perf but
> wasn't able to see anything interesting (just like the sem_post
> function wasn't taking any CPU time) but I must say there are lots of
> HW counters I don't know how to use.
> 
> Could it be possible to control the behavior of the syscall function
> ? Because the executable that shows that issue is also linked with
> some code I've no control on.

Start by using strace -ff -ttt to get timings for everything, and 
then look at how long the syscalls took and if that relates in 
any way to the behaviour you're seeing.

Cheers,
Carlos.