Re: HT Benchmarks (was: /proc/cpuinfo and hyperthreading)

[Andrew Burgess <aab@cichlid.com>]

>Number of threads	Elapsed time   User Time   System Time
>1                   53:216           53:220    00:000
>2                   29:272           58:180    00:320
>3                   27:162         1:21:450    00:540
>4                   25:094         1:41:080    01:250

>Elapsed is measured by the parent thread, that is not doing anything
>but wait on a pthread_join. User and system times are the sum of
>times for all the children threads, that do real work.

>The jump from 1->2 threads is fine, the one from 2->4 is ridiculous...
>I have my cpus doubled but each one has half the pipelining for floating
>point...see the user cpu time increased due to 'worst' processors and
>cache pollution on each package.

>So, IMHO and for my apps, HyperThreading is just a bad joke.

Why do you care about user time? The elapsed time went down by
4 minutes (2->4 threads), if that's a joke I don't get it :-)

New Intel Ad: "What are you going to do with your 4 minutes today?"