getrusage vs clock

paul zimmermann Paul.Zimmermann at
Thu Jan 21 13:02:39 UTC 2016

>   since version 2.18 of the glibc, the clock() function is much more precise.
>   For example on my machine it has a resolution of 1 micro-seconds whereas
>   getrusage() has a resolution of 4ms only, as demonstrated by the program
>   below:
> I believe we already use clock_gettime(2) directly on GNU/Linux, which
> is the underlying syscall that clock(3) uses in newer GNU libc versions.
> Does that not happen in your tests?

I don't know how to check which function is used. With gmp-6.1.0 on my
workstation I get:

zimmerma at tomate:/tmp/gmp-6.1.0/tune$ ./speed
CPU cycle counter, supplemented by microsecond getrusage()
Gnuplot home page
Quickplot home page

which lets me think that getrusage() is still used.


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