Re: [PATCH] CPU time clock support in clock_* syscalls

[Christoph Lameter]

On Tue, 5 Oct 2004, Roland McGrath wrote:

> > I just reviewed the code and to my surprise the simple things like
> >
> > clock_gettime(CLOCK_PROCESS_CPUTIME_ID) and
> > clock_gettime(CLOCK_THREAD_CPUTIME_ID) are not supported.
>
> You seem to be confused.  A clockid_t for a CPU clock encodes a PID, which
> can be zero to indicate the current thread or current process.

Is there a standard for that? Or is it an opaque type that you have
defined this way?

> > The thread specific time measurements have nothing to do with the posix
> > standard and may best be kept separate.
>
> Nonsense.  POSIX defines the notion of CPU clocks for these calls, and that
> is what I have implemented.

Posix only defines a process and a thread clock. This is much more.

> Of course glibc is in charge of what the meaning of the POSIX APIs is.
> That is true for every call.

The proper information to realize these clocks is only available on the
kernel level. A clean API for that would remove lots of code that
currently exists in glibc.

I wonder how glibc will realize access to special timer hardware. Will
glibc be able load device drivers for timer chips?

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