Davide Libenzi wrote: > It sucks when seen from a micro-bench POV, but does it really matter > overall? The vast majority of software usually calls > sysconf(_SC_NPROCESSORS_*) with very little frequency (mostly once at > initialization time) anyway. That's what 50us / call?
This is not today's situation. Yes, 10 years ago when I added the support to glibc it wasn't much of a problem. But times change. As I said before in this thread, OpenMP by default scales the number of threads used for a parallel loops depending on the number of available processors/cores and therefore the number must be retrieved every time (with perhaps minimal caching of a few secs, but this requires gettimeofday calls...). All of a sudden this is not micro benchmark anymore. It's a real issue which we only became aware of because it is noticeable in real life. -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
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