HT Benchmarks (was: /proc/cpuinfo and hyperthreading)
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Quoted 10 lines
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 01:250Elapsed 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.
Quoted 6 lines
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?"
Quoted 15 lines · On 2002.12.18 Andrew Burgess wrote:
Quoted 14 lines
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 01:250Elapsed 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.
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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...
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J.A. Magallon <[email protected]> \ 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))