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Message-ID: <20120926114522.GA4627@cmpxchg8b.com>
Date: Wed, 26 Sep 2012 13:45:22 +0200
From: Tavis Ormandy <taviso@...xchg8b.com>
To: john-dev@...ts.openwall.com
Subject: choosing code optimisations
Hey, just in case anybody else wants to try it with their formats, here is a
quick note on finding low hanging performance wins for gcc. I've been using the
attached script to benchmark different options, it turns out
prefetch-loop-arrays is a pretty major win for raw-sha1-ng, so I include:
#pragma GCC optimize "-fprefetch-loop-arrays"
Here is an example for raw-md5, a default build of jumbo7 with
linux-x86-64-native produces this:
$ ../run/john --test --format=raw-md5
Benchmarking: Raw MD5 [128/128 SSE2 intrinsics 4x]... DONE
Raw: 17693K c/s real, 17693K c/s virtual
$ bash ~/chooseopts.sh linux-x86-64-native rawMD5_fmt_plug.c raw-md5 | sort -g | tail
Raw: 17971K c/s real, 18025K c/s virtual -fno-regmove
Raw: 18033K c/s real, 18105K c/s virtual -fschedule-insns
Raw: 18039K c/s real, 18075K c/s virtual -falign-loops
Raw: 18052K c/s real, 18106K c/s virtual -fno-forward-propagate
Raw: 18072K c/s real, 18108K c/s virtual -fno-tree-loop-optimize
Raw: 18092K c/s real, 18146K c/s virtual -fno-guess-branch-probability
Raw: 18158K c/s real, 18194K c/s virtual -fno-reorder-blocks
Raw: 18168K c/s real, 18223K c/s virtual -fno-tree-ch
Raw: 18185K c/s real, 18221K c/s virtual -fno-if-conversion
Raw: 18516K c/s real, 18553K c/s virtual -fno-tree-ter
So -ftree-ter (enabled by default) sounds like it's hurting a lot...
$ sed -i '1i#pragma GCC optimize "-fno-tree-ter"' rawMD5_fmt_plug.c
$ make clean linux-x86-64-native
$ ../run/john --test --format=raw-md5
Benchmarking: Raw MD5 [128/128 SSE2 intrinsics 4x]... DONE
Raw: 18484K c/s real, 18484K c/s virtual
Nearly 1M c/s for free, maybe you want to guard it with gcc major/minor version
checks, but it seems too good to ignore. Here is the default output for nt:
$ ../run/john --test --format=nt
Benchmarking: NT MD4 [128/128 X2 SSE2-16]... DONE
Raw: 37253K c/s real, 37253K c/s virtual
$ bash ~/chooseopts.sh linux-x86-64-native nt2_fmt_plug.c nt | sort -g | tail
Raw: 38596K c/s real, 38596K c/s virtual -fno-tree-loop-optimize
Raw: 38709K c/s real, 39100K c/s virtual -fno-strict-aliasing
Raw: 38822K c/s real, 39214K c/s virtual -fno-optimize-register-move
Raw: 38822K c/s real, 39214K c/s virtual -fno-regmove
Raw: 38846K c/s real, 39239K c/s virtual -fnon-call-exceptions
Raw: 38955K c/s real, 39348K c/s virtual -fno-reorder-blocks
Raw: 39007K c/s real, 39007K c/s virtual -fno-tree-ter
Raw: 39326K c/s real, 39326K c/s virtual -freorder-blocks-and-partition
Raw: 39343K c/s real, 39740K c/s virtual -fno-crossjumping
Raw: 39373K c/s real, 39373K c/s virtual -fno-guess-branch-probability
Unexpected, but -fguess-branch-probability doesn't seem helpful:
$ sed -i '1i#pragma GCC optimize "-fno-guess-branch-probability"' nt2_fmt_plug.c
$ make clean linux-x86-64-native
$ ../run/john --test --format=nt
Benchmarking: NT MD4 [128/128 X2 SSE2-16]... DONE
Raw: 39428K c/s real, 39428K c/s virtual
A free 2.2M c/s improvement.
Tavis.
--
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taviso@...xchg8b.com | pgp encrypted mail preferred
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Download attachment "chooseopts.sh" of type "application/x-sh" (1419 bytes)
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