Author: Vincent Diepeveen
Date: 05:21:42 04/13/03
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On April 13, 2003 at 02:37:57, Tom Kerrigan wrote: >On April 13, 2003 at 01:04:52, Robert Hyatt wrote: > >>It _is_ pinned on SMT. The two logical processors are producing wildly >>imbalanced results when using threads, vs using two separate processes. It >>would appear to be cache-related... > >This is some sort of joke, right? You and Vincent see the same behavior, you >have SMT and Vincent doesn't, and somehow the problem is with SMT? > >How much of the time are your threads idle, out of curiosity? If one thread is >idle much more than the other, then of course that is going to skew your NPS. > >-Tom Of course both Crafty and DIEP are using YBW. I didn't checkout what bob does here, but in past in DIEP i used to always let process 0 let the search start. Nowadays that is not the case. The i/o thread picks the first process it can get. All search processes are completely identical. This process then is starting the search. That means the other CPUs idle when this process starts the search. In crafty that's also the case, but i do not know whether Bob always picks a certain thread as first. If so then that might explain quite something. Measuring idle time with SMT is very hard to do objective, but of course you can relatively check it out. Basically the problem is you do not know what the maximum % is that i can get out of SMT, because it is dependant upon the other process too.
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