On Fri, Jul 28, 2017 at 09:58:54AM +0100, James Cowgill wrote: > On 28/07/17 09:05, Richard Braun wrote: > > On Thu, Jul 27, 2017 at 11:39:21PM +0100, James Cowgill wrote: > >> While debugging a timing problem with FFmpeg on Hurd, I noticed that the > >> "clock" function has a far lower precision on Hurd than it does on > >> Linux, even though CLOCKS_PER_SEC is 1000000 on both. Why is this? > >> > >> I also found this patch to libc which may be responsible: > >> hurd-i386/unsubmitted-clock_t_centiseconds.diff > >> > >> I'm not entirely sure why patching libc is appropriate to fix the > >> claimed issues. > > > > The patch has nothing to do with precision. The kernel simply doesn't > > have any high resolution timing system, whereas Linux does. > > In that case, clock should be returning multiples of whatever precision > is supported by the kernel so that CLOCKS_PER_SEC is still correct.
That macro is required by XSI to have this value, as described by POSIX [1]. -- Richard Braun [1] http://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html
