Re: [PATCH] - sched_clock() broken for ia64 SN platform

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2003-11-20 12:24:08
>>>>> On Wed, 19 Nov 2003 16:56:23 -0800 (PST), John Hawkes <hawkes@babylon.engr.sgi.com> said:

  John> We might instead want to implement a more general scheme,
  John> along the lines of what is done by (struct time_interpolator),
  John> to provide a framework to solve this for other architectures
  John> that have "drifty" non-default timebases.

My sense is that with a bit of thinking, it would be possible to come
up with a solution that allows even drifty platforms to use ITC for
sched_clock()---it serves very a specific purpose in the scheduler and
scalability is key and perfect accuracy is not (unlike for
gettimeofday).  I don't think anything that goes out to read a single
(shared) platform counter will be sufficiently scalable to the number
of CPUs you guys are talking about.  But yes, it would be much more
effort than just adding Yet Another Callback.  The rewards would be
bigger, though, too...

	--david
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Received on Wed Nov 19 20:24:28 2003

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