Author: Keith Evans
Date: 21:44:34 07/15/03
Go up one level in this thread
On July 16, 2003 at 00:29:43, Robert Hyatt wrote: >On July 16, 2003 at 00:05:29, Keith Evans wrote: > >>On July 15, 2003 at 23:35:30, Robert Hyatt wrote: >> >>>On July 15, 2003 at 23:05:37, Vincent Diepeveen wrote: >>> >>>> >>>> >>>>Now i can disproof again the 130ns figure that Bob keeps giving here for dual >>>>machines and something even faster than that for single cpu (up to 60ns or >>>>something). Then i'm sure he'll be modifying soon his statement something like >>>>to "that it is not interesting to know the time of a hashtable lookup, because >>>>that is not interesting to know; instead the only scientific intersting thing is >>>>to know is how much bandwidth a machine can actually achieve". >>>> >>> >>> >>>What is _interesting_ is the fact that you are incapable of even recalling >>>the numbers I posted. >>> >>>to wit: >>> >>>dual xeon 2.8ghz, 400mhz FSB. 149ns latency >>> >>>PIII/750 laptop, SDRAM. 125ns. >>> >>>Aaron posted the 60+ ns numbers for his overclocked athlon. I assume his >>>numbers are as accurate as mine since he _did_ run lm_bench, rather than >>>something with potential bugs. >>> >>>I can post bandwidth numbers if you want, but that has nothing to do with >>>latency, as those of us understanding architecture already know. >>> >> >>Can you run lmbench and give the latency numbers for different stride sizes? >>Then you could quote numbers from cache,... >> > >Here's my laptop data. L1 seems to be 4 clocks. L2 9 clocks, memory >at 130ns. This is a PIII/750mhs machine with SDRAM. I just ran it again >to produce these numbers. > > > >Host OS Mhz L1 $ L2 $ Main mem Guesses >--------- ------------- --- ---- ---- -------- ------- >scrappy Linux 2.4.20 744 4.0370 9.4300 130.2 > >>In the lmbench paper they have a nice graph like this. > > >Is the above what you want? I think that it's as close as you're going to get. The most important thing is that 130 [ns] is the largest number. And wouldn't that be a little bit pessimistic even for chess hash tables?
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