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Re: Issue #1429 et al, WAS: RE: Paul, info for releasing 0.28

From: Tobias Ringström <tobias_at_ringstrom.mine.nu>
Date: 2003-08-24 22:21:10 CEST

Sander Striker wrote:
> Another thing is the md5 checksums. We might want to think about a
> little less CPU intensive algorithm, since this one is up there aswell.
> MD5Transform (which is internal to apr, called by apr_md5_update) is taking
> ~15% of total checkout time over ra_local. It's at the very top of the
> flat profile.

This data surprised me, so I did some testing that might be of interest.
I added code to apr-util to count the number of bytes summed, and for
your test case, which contains around 290 MiB data, I found that 1181
MiB was summed (using svn from trunk). I am not familiar with the use of
checksums in subversion, but it might be possible to reduce the amount
of summing.

Openssl has a nice speed test for its algorithms, and for MD5 I get the
following (using "openssl speed md5"):

> The 'numbers' are in 1000s of bytes per second processed.
> 16 bytes 64 bytes 256 bytes 1024 bytes 8192 bytes
> 13938.39k 48742.55k 142615.89k 277656.06k 379101.18k

In other words, it sums hundreds of megabytes per second. This openssl
(from RedHat Linux 9) was compiled with -DMD5_ASM, and I'm running it on
an Athlon XP 2700+ with Linux 2.6.0-test4.

/Tobias

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Received on Sun Aug 24 22:22:00 2003

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