Author: Joachim Rang
Date: 03:05:15 04/15/04
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On April 14, 2004 at 22:49:39, Robert Hyatt wrote: >I just finished some HT on / HT off tests to see how things have changed in >Crafty since some of the recent NUMA-related memory changes that were made. > >Point 1. HT now speeds Crafty up between 5 and 10% max. A year ago this was >30%. What did I learn? Nothing new. Memory waits benefit HT. Eugene and I >worked on removing several shared memory interactions which led to better cache >utilization, less cache invalidates (very slow) and improved performance a good >bit. But at the same time, now HT doesn't have the excessive memory waits it >had before and so the speedup is not as good. > >Point 2. HT now actually slows things down due to SMP overhead. IE I lose 30% >per CPU, roughly, due to SMP overhead. HT now only gives 5-10% back. This is a >net loss. I am now running my dual with HT disabled... > >More as I get more data... Here is two data points however: > >pos1. cpus=2 (no HT) NPS = 2.07M time=18.13 > cpus=4 NPS = 2.08M time=28.76 > >pos2. cpus=2 NPS = 1.87M time=58.48 > cpus=4 NPS = 2.01M time=66.00 > >First pos HT helps almost none in NPS, costs 10 seconds in search overhead. >Ugly. Position 2 gives about 5% more nps, but again the SMP overhead washes >that out and there is a net loss. I should run the speedup tests several times, >but the NPS numbers don't change much, and the speedup could change. But this >offers enough.. In a german Board someone postetd figures for the Fritzmark of Fritz 8. Fritz gains still 25% form HT (in this specific position) cpus=2 NPS = 2.35 cpus=4 NPS = 2,95 I have unfortunately no information about search time. Does that mean Fritz 8 is poorly optimized? regards Joachim
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