Re: Debian Hurd clock precision
On Fri, Jul 28, 2017 at 11:10:29AM +0200, Richard Braun wrote:
> 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].
I replied too quickly. I don't have all the details in mind but you may
be right. Please use the bug-hurd@gnu.org mailing list to report this
issue upstream.
--
Richard Braun
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