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Re: [glibc] Fix Linux sysconf(_SC_NPROCESSORS_[CONF|ONLN]) performanceproblem


Am 06/16/11 20:25, schrieb Linus Torvalds:
On Thu, Jun 16, 2011 at 1:04 PM, Paul Eggert<eggert@cs.ucla.edu> wrote:

"Stale" could mean "the tv_sec value doesn't match", or it could be something fancier; I doubt whether it matters much.

I certainly think that would be a lot better than what glibc does now - at least limiting the /proc/stat reading to a maximum of once per second or similar.

And it could be combined with the patch I just sent out (which ends up
parsing /sys/devices/system/cpu/online every time. It's a cheaper (and
more obvious) file than /proc/stat, but it's still not zero-cost.

Linus

As, at least today, most users run with a constant number of cpus,
how about a configure option like num_of_cpus_may_vary in either kernel or glibc.


This would give the time to discuss calmly a better solution for the others.

--
Klaus


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