Author: Frank Phillips
Date: 12:29:37 12/19/03
Go up one level in this thread
On December 19, 2003 at 12:15:37, Robert Hyatt wrote: >On December 19, 2003 at 10:52:57, Anthony Cozzie wrote: > >>On December 19, 2003 at 10:41:27, Robert Hyatt wrote: >> >>>On December 19, 2003 at 01:21:45, Jouni Uski wrote: >>> >>>>After installing more RAM to my Pentium 2,4 GHz I tested Fritz8 in some test >>>>suites with 128MB and 384MB hash (time limit was 10 minutes and positions quite >>>>hard = average solution times around 3-5 minutes): to my surprise >>>>average solution time was shorter with 128MB! Why? Absolutely no hard disk >>>>swapping with 512MB total RAM! >>>> >>>>Jouni >>> >>> >>>Hashing is based on random numbers. Which means the result of using them >>>is going to have a bit of randomness as well. Sometimes bigger hash slows >>>a program down, because it makes the search more accurate, which might make >>>it a bit slower. But accuracy and speed don't necessarily match up so it is >>>not easy to say "this is slower, so it is worse." >>> >>>Also, there are hardware considerations. The size of the TLB for example. >>>If you blow that out, you make your memory access time go from maybe 150ns >>>to 3X that. Since hash tables are addressed randomly, this is a real >>>possibility. IE the opteron I was using earlier this week has just over >>>1000 TLB entries. That lets me address 1000 * 4K very quickly. Anything >>>beyond that sees slower memory access times. >> >>there is a patch for 2.6 that will automatically use the large pages. that plus >>prefetching should give quite a speedup to crafty . . . >> >>anthony > >I know. I have mentioned that in the past already. However, on my xeon, the >usual memory benchmark program only reports something like 60 TLB entries, >which seems low (lmbench). I have not tried 2.6 on my machine, as it isn't >just a matter of grabbing and building the kernel, there are a bunch of other >things including binutils, and the like, that also have to be upgraded. I hope >someone will do a 2.6 distribution before long and I'll dive in. > >the 4M page size sounds pretty good, from a memory access point of view (not >thrashing the TLB so badly). Mandrake have cooker (testing) singal CD out, based on the 2.6 pre-kernel and other bleeding edge stuff.
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