Author: Tom Kerrigan
Date: 14:12:05 08/22/04
Go up one level in this thread
On August 22, 2004 at 11:10:33, Robert Hyatt wrote: >Simple. I access a batch of random attack entries. I then access a _lot_ of >other stuff before I come back to the attack entries. Your 256K cache has 4K >lines. I don't know what the set associativity is, as AMD has lots of options >there in recent history. But that further reduces the number of "buckets" to >stuff stuff in. My xeon claims 16-way set associativity, with 128 byte lines. >That turns into a paultry 256 sets. It is very easy to get a bad physical >memory layout where you don't even use all of those sets, and where some sets >get badly overloaded. This is a bunch of nonsense. You make it sound like associativity somehow decreases the amount of cache you have. Really, associativity has no place in this discussion, except maybe to note that it reduces the behavior that you're complaining about, namely random accesses evicting important data from the cache. But let's say you do randomly access your working set. How about you explain how performance isn't increased going from 256k to 512k cache? You're randomly accessing a bigger random subset of your working set. (And really, 512k is a large percentage of your maximum possible working set... Windows reports that it only allocates 5MB for Crafty, including hash tables, tables that never get used, code that isn't part of the search, memory for the stack, etc.) -Tom
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