Dirk Eibach wrote: > [EMAIL PROTECTED] wrote: >> On 8/17/07, Dirk Eibach <[EMAIL PROTECTED]> wrote: >>> [EMAIL PROTECTED] wrote: >>>> Dirk Eibach wrote: >>>> > Hello, >>>> > >>>> > I'm wondering how long a rt_mutex_acquire is supposed to take on a >>>> PPC405 >>>> > platform. I'm getting times about 50 usec here, which is too much for my >>>> > application. Is anything wrong in my kernel/xenomai configuration or is >>>> > this time to expected? >>>> >>>> How do you measure this ? Are you sure the mutex is free when you try to >>>> acquire it ? >>>> >>> I prepared a small testcase. It shows about 8.300 ticks, which is about 30 >>> usec on my platform (266MHz). >> Did you try to call ppc_getcounter twice in a raw to measure the >> overhead of this function ? > > Calling ppc_getcounter twice in a raw results in 116 ticks.
Is that service RT-safe, means does it stay in user space and issue no Linux syscall? Maybe some of the PPC gurus can comment on this as well (/me is lacking comparative numbers). Besides this, you may want to try running the latency tracer on your scenario. xntrace_user_start() and xntrace_user_stop(0) would frame the path you want to measure, /proc/ipipe/trace/frozen will show its kernel side. For sure, that tool will increase the latency even more, but it may show better what goes on. Jan
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