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Re: AES performance results



On 2/26/07, Nick Mathewson <nickm@xxxxxxxxxxxxx> wrote:
METHODOLOGY: I wrote a stupid benchmark function in aes.c to encrypt a
million cell-sized chunks using our aes_crypt function, and timed it
with the unix "time" command.  I did this twice for each
(computer,code) pair, I took the median of three runs.

You have to be very careful of cache issues with micro-benchmarks like that. I'm think that you're ok because the cache profile of an AES function is probably pretty much fixed (it walks the input and the output and the tables are of fixed size I'm guessing). But if the faster impl uses different sized tables etc (or more code, looking at FULL_UNROLL) you might find that, when running with the rest of the Tor code, the results are rather different.


AGL

--
Adam Langley                                      agl@xxxxxxxxxxxxxxxxxx
http://www.imperialviolet.org                       650-283-9641