Author: J. Wesley Cleveland
Date: 12:21:35 07/18/03
Go up one level in this thread
On July 17, 2003 at 18:25:51, Robert Hyatt wrote: >On July 17, 2003 at 17:35:33, Dieter Buerssner wrote: > [snip] >> >>I cannot find any randomness in the reads of lm-bench (I downloaded latest >>stable source today, not the experimental version, available, too). If it would >>do random reads, it would have no way to avoid the problem with the TLBs you >>explained. > >4M pages solves it for at least 250mb worth of RAM. But then again, _no_ chess >program depends on purely random memory accesses to blow out the TLB. The only >truly random accesses I do are the regular hashing and pawn hashing, which >both total to significantly less than the total nodes I search. Which means >the TLB penalty is not even 1% of my total run time. Probably closer to >.01% - .05%. > >I ignore that. Why do you think it is that low? I get ~20-30% of nodes have hash probes with crafty. If you are getting 1m nodes/sec, then this is a probe every 3-5 usec. With a very large hash table and 4K pages, the large majority of these will cause a TLB miss. At 200 nsec each (a guess), this could be up to 5% of your total run time. [snip]
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