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SubjectRe: pipe performance regression on ia64
>>>>> 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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