[rescue] OS X and dual CPU machines?

r.stricklin bear at typewritten.org
Mon Jun 9 10:27:10 CDT 2003

On Monday, June 9, 2003, at 12:38  AM, Curtis H. Wilbar Jr. wrote:

>> Single thread: 4.23 seconds.
>> Two threads:  18.915 seconds.
>> Clearly something suboptimal is happening.
> what could be happening is that there is one lock around one (or both
> of those devices).... how a MP machine behaves with this test is
> irrelevant to real world usage.

I agree completely that it's fairly irrelevant to real-world usage.

But I would argue that it taking consistently four times as long to run 
two fhlushstones in parallel than it does to run one would tend to 
indicate something peculiar going on. IRIX 6.5 had a similar problem 
with IP19 when you got to more than two CPUs and three fhlushstones. 
Suddenly it would hit a wall and things started taking three or four 
times longer to run. They fixed it around 6.5.12 (read the release 

You'll find that even on SunOS 4.1.4 two parallel fhlushstones run in 
1.7x a single fhlushstone. This was on a 4x RT605 4/670, not exactly 

Also, I apologize for using the term 'threading' in a haphazard manner 
in my last message.


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