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

[J.A. Magallon]

On 2002.12.18 Andrew Burgess wrote:
>>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?"
>

Of course I gain something. The problem is the price you pay for the
gain.

Prices in Spain: a P4 with 512Kb cache, 210 euros. Equal features (freq,
cache), but Xeon version, 320 euros. So you pay 50% more money for
10% more performance. Not too fair...

-- 
J.A. Magallon <[e-mail]>      \                 Software is like sex:
werewolf.able.es                         \           It's better when it's free
Mandrake Linux release 9.1 (Cooker) for i586
Linux 2.4.20-jam2 (gcc 3.2 (Mandrake Linux 9.1 3.2-4mdk))