Re: Measure time
george anzinger <[email protected]>
| Newsgroups | org.kernel.vger.linux-gcc,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
Der Herr Hofrat wrote: > > > > > Hi, > > > > ftime() will return milliseconds, but it's considered an obsolete function. > > You could use gettimeofday() (as Richard Johnson suggested) to get > > microseconds and divide them to get milliseconds, although I don't know how > > time critical your routines are. > > > > If you're still looking for nanoseconds, I'm told you can use > > clock_gettime() but it's still quite unavailable (I've never seen it myself, > > yet).. however even if it was available you possibly wouldn't get a very > > high resolution from it with current systems.. > > > clock_gettime() is available in the hard realtime extensions like RTLinux . > The clock resolution is limited to 32ns though - and atleast on X86 I don't > think there is a way to get below that. The high-res-timers patch provides clock_gettime() with resolution to the TSC increment. But you need to understand that this is a system call which can take on the order of 1000 or these units. Add in a little cach hit/ miss and interrupt randomness and well... Still, there it is. Check out the web site below. -- George Anzinger [email protected] High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml