Re: pipe performance regression on ia64

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2005-01-20 04:31:05
>>>>> On Wed, 19 Jan 2005 23:43:45 +1100, Nick Piggin <nickpiggin@yahoo.com.au> said:

  Nick> Oh that's quite true. A bad score on SMP on the pipe benchmark
  Nick> does not mean anything is broken.

  Nick> And IMO, probably many (most?) lmbench tests should be run
  Nick> with all processes bound to the same CPU on SMP systems to get
  Nick> the best repeatability and an indication of the basic serial
  Nick> speed of the operation (which AFAIK is what they aim to
  Nick> measure).

We need to keep an eye on both the intra- and the inter-cpu
pipe-bandwidth and should measure them explicitly.  The problem is
that at the moment, we get one, the other, or a mixture of the two,
subject to the vagaries of the scheduler.  If we could reliably
measure both intra and inter-cpu cases, we may well find new
optimization opportunities (I'm almost certain that's the case for the
cross-cpu case; which is probably the more important case, actually).

	--david
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Received on Wed Jan 19 12:36:21 2005

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