Re: Debian Hurd clock precision
James Cowgill, on ven. 28 juil. 2017 09:58:54 +0100, 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.
The problem is that applications use it to determine in what units are
the values in /proc/ , and others assume 100 there. So we're stuck with
100 in all of this.
Samuel
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