Author: David Rasmussen
Date: 13:19:01 01/16/03
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On January 16, 2003 at 16:09:41, Scott Gasch wrote: > >Assuming you are running XP/2k take a look at perfmon.exe. I suggest you have a >look at the following counters: > XP. Thanks, I didn't know perfmon. >Process | Page Faults/sec (for yourengine.exe) >Process | I/O Read Bytes/sec (for yourengine.exe) >Process | Working Set >Process | Private Bytes >Cache | Fast Reads/sec >Cache | Fast Read Not Possible/sec >Cache | Read Aheads/sec >Memory | Page Faults/sec > >One theory: Your OS is under memory pressure (how many bytes free when you are >running your engine in a normal position) and has reduced the working set size >of yourengine.exe to compensate. The part that it paged out is your EGTB cache >because "well, yourengine.exe doesn't seem to be touching this memory, let's >trim". Everything is fine when you are playing non endgame positions but as >soon as you get into an endgame you start probing. That is I/O to the EGTB >files but also the EGTB code suddenly wants to touch the EGTB cache. Well the >kernel is now taking page faults and swapping in the EGTB cache. Double whammy. > >I don't suspect cacheman performance as a culpret here, I am more inclined to >suspect memory pressure and working set trimming on a 256Mb machine. > >You want your engine to be taking VERY VERY few page faults if any while >searching. Personally I lock my transposition table into main memory and tell >the OS do *not* swap any of this. See VirtualLock on windows. You need admin >privileges to do this and you may have to call SetProcessWorkingSet before the >call succeeds. You might try locking your EGTB cache into memory as well if you >find that yourengine.exe is taking a lot of page faults while probing. > According to perfmon, in the first second or so, there are some page faults, but as soon as everything is "up and running", it stays flat on zero. So I guess that's not the problem. I/O read bytes is maxed to 100, scale 1,000. I didn't try the others. What is "working set"? /David
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