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Which system hardware timer does clock_gettime function in linux use internally to give nano seconds level resolution back to the user code when invoked to measure elapsed time for a given segment of code ?

Soumajit
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  • You should have a look at the manpage of [`clock_gettime`](http://linux.die.net/man/3/clock_gettime). – Nidhoegger May 04 '15 at 14:09
  • [How is the microsecond time of linux gettimeofday() obtained and what is its accuracy?](http://stackoverflow.com/q/13230719/1504523) may shed some light on the scheme. – Arno May 04 '15 at 15:47
  • IIRC, Linux cannot give ns resolution. – edmz May 05 '15 at 11:29

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Modern CPUs run at several GHz clock frequency. A frequency of 1 GHz equals a clock period of 1 ns. So running a (wide) counter at 1 GHz gives a time resolution in nanoseconds. This does not mean that the time is as accurate as it is displayed. The value has just such a high resolution.

Paebbels
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