Author: Tom Kerrigan
Date: 03:06:24 08/25/04
Go up one level in this thread
Here's your first experiment, cache misses per node:
=== cache misses per node ===
size inst data total
128K 0.36 7.66 8.05
256K 0.21 3.33 3.54
512K 0.04 2.00 2.04
1M 0.04 1.28 1.32
2M 0.04 1.05 1.09
Now here's your new data, same thing:
=== cache misses per node ===
size inst data total
128K 0.71 4.33 5.04
256K 0.68 1.92 2.60
512K 0.00 0.46 0.46
1M 0.00 0.15 0.15
2M 0.00 0.00 0.00
Let's go back to your little wager:
>I can do that and will report the results later. Want to wager whether it
>changes things or not with respect to my working set size estimations???
>Think about it before you answer.
Too bad you posted the data before I answered, because I would have taken this
bet and won. As you can see from the tables, your first set of data completely
misrepresents the number of cache misses that occur during search once the cache
is warmed up.
If you plot the total misses, your 1st experiment showed a gradual decline in
misses as cache size increased, so it's easy to conclude that your working set
is "big." Thankfully we have this new data, which shows a huge dropoff between
the 256k and 512k numbers. So yes, this should definitely change your working
set size esimations. It surprises me that it hasn't, but then again, I
understand that you have your fragile ego to protect.
BTW, I estimate that Crafty does around 400 data memory accesses per node:
(2GHz / 1.2M NPS) * 25% (conventional wisdom)
So even if you have the relatively high number of 4 misses per node, you're
still getting a 99% hit rate. I'd hardly call that thrashing the cache with all
sorts of random accesses, which is what you've been claiming Crafty does.
-Tom
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