Author: Robert Hyatt
Date: 10:15:36 12/17/02
Go up one level in this thread
On December 17, 2002 at 11:58:21, Gian-Carlo Pascutto wrote: >On December 17, 2002 at 11:27:18, Matt Taylor wrote: > >>Crafty gets better results with HT, > >In addition to what Vincent said, the data we currently >have is saying exactly the opposite. > I don't follow. I posted the following twice already: 1 thread, SMT disabled, 24 positions, run twice, 1001.5K nps 2 threads, SMT disabled, same conditions, 1604.5K nps 3 threads, SMT enabled, same conditions, 1820.25K nps 4 threads, SMT enabled, same conditions, 1923.0K nps Hyperthreading took the 16.04.5K nps for two bare xeon processors and improved that by 20%. I can certainly post the raw data if it is important. I believe 20% is definitely better than 11%. And 20% is not something to wave off as unimportant. >So I'd like to know what you based that statement on. > >Magic 8-ball? > >>but it's been optimized for HT. > >It's not - even Robert will tell you this. Actually it has. But the optimization didn't make a huge difference. It turns out that my spinwaits, which are the main problem, are complex enough that the pause doesn't help much. I don't spin on a single volatile int, I spin and test several, which prevents the big problem that a single spin sees without a pause thrown in. > >-- >GCP
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