Hyperthreading and Task number Impact Observations
Over the next couple of days I plan to generate some observations on the execution time and aggregate throughput impact of switching my Westmere E5620 between hyperthreaded and not, and of varying the number of simultaneously executing Einstein HF 3.06 tasks.
Westmere is mostly a 32nm Xeon flavor of the classic Nehalem 4-core design, but with a 12 M L3 cache. For these tests I'll leave it running as it has been lately, with a moderate overclock of 3.42 GHz, with 4 Gbyte of RAM running at default settings (and one more Gbyte plugged in not currently actually recognized by the BIOS--oops).
My current intentions--subject to revision if I have a better thought or get better advice here:
1. One "measurement task" for each condition, will be started only after the remaining tasks for the condition are up and running, and will all be chosen from the same HF frequency 1373.90.
2. I'll turn off most overhead tasks of the more frivolous sort, and not use the system for personal work during the timed runs, but leave running my Kaspersky AV (which does hurt a bit during that nasty slow startup phase, but I consider essential).
The test conditions I definitely plan to log are:
I might fill in some of the intermediate task count points, say perhaps HT 4 and HT 6, but probably not all of them.
For each condition I think I'll show CPU time for the task, CPU time for the task relative to the HT_8 case, and implied system throughput relative to the HT_8 case. Also system input power.
Why bother? On the negative side, since these results are rather strongly influenced by the particular CPU design, by the application being run, by some other system design and configuration details, and by the other code executing on the system they won't generalize very far.
But I think some of the results may surprise people--for example those who may expect a single Einstein task running HT to run about as fast as the single nHT case, or people who expect a full doubling of aggregate throughput with HT application.
My target is not mostly the regular posters here, for whom few of my results will be surprising, but mostly others who drop by who may be less well informed.
I don't think thread starters own threads, but I'd be perfectly pleased if others with useful observation data saw fit to add to this thread.
While my timing in starting this thread and project was influenced by this other thread I don't regard this as an answer to or continuation of that one.