Re: Timer updates revision 7 (asm sets predicates/various fixes)

David Mosberger
2004-08-02T09:36:17Z

>>>>> On Fri, 30 Jul 2004 08:34:56 -0700 (PDT), Christoph Lameter <clameter@sgi.com> said:

>> The numbers above indicate a substantial slowdown going from 1 to
>> 2 cpus. What happens at higher cpu counts.

Christoph> The code that uses cmpxchg will always be a scalability
Christoph> issue.

Also, you need to keep things in perspective: the test programs
_continually_ bangs on gettimeofday(). If the cmpxchg were a
scalability issue for, say, 16-32-way machines with _real_ workloads,
I'd really be surprised. Now if you have 128 or more CPUs, I do agree
that the picture would be very different and scalability is a much
bigger concern.

--david