Re: [time] add support for CLOCK_THREAD_CPUTIME_ID andCLOCK_PROCESS_CPUTIME_ID

[Christoph Lameter]

On Fri, 24 Sep 2004, Ulrich Drepper wrote:

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> Christoph Lameter wrote:
>
> > Then please sign off on the following patch:
>
> Sorry, I fail to see the point.  The CPUTIME stuff will either way be
> entire implemented at userlevel.  If we use TSC, we compute the
> resolution from the CPU clock speed (no need to comment, I know it's not
> reliable everywhere).  If we fall back on realtime, we will simply in
> glibc map

I thought I heard you asking for CPUTIME returning the actual cputime
used in the last message. I have proposed falling back to realtime in the
past but that was not acceptable.

>
>    clock_getres (CLOCK_PROCESS_CPUTIME_ID, &ts)
>
> to
>
>    clock_getres (CLOCK_REALTIME, &ts)
>
> The kernel knows nothing about this clock.

Yes and glibc will have to get through contortions to
simulate a clock that returns the actual cpu time used. Why not cleanly
do the clock_gettime syscall without doing any redirection of clocks?

Any implementation of the CPUTIME clocks is always easier to do in the
kernel with just a few lines.

> The comment changes are OK, of course.
>
> If there is more to change this is in glibc.  So far I have not heard of
> anybody wanting to use the clocks this way.  This is why we do not have
> the fallback to realtime implemented.  If you say you need it I have no
> problem adding appropriate patches.

Ok, I will dig out my old patch and repost it to glibc-alpha.
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