44 lines
1.6 KiB
Text
44 lines
1.6 KiB
Text
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This is a patched version of zlib modified to use
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Pentium-optimized assembly code in the deflation algorithm. The files
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changed/added by this patch are:
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README.586
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match.S
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The effectiveness of these modifications is a bit marginal, as the the
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program's bottleneck seems to be mostly L1-cache contention, for which
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there is no real way to work around without rewriting the basic
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algorithm. The speedup on average is around 5-10% (which is generally
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less than the amount of variance between subsequent executions).
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However, when used at level 9 compression, the cache contention can
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drop enough for the assembly version to achieve 10-20% speedup (and
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sometimes more, depending on the amount of overall redundancy in the
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files). Even here, though, cache contention can still be the limiting
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factor, depending on the nature of the program using the zlib library.
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This may also mean that better improvements will be seen on a Pentium
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with MMX, which suffers much less from L1-cache contention, but I have
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not yet verified this.
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Note that this code has been tailored for the Pentium in particular,
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and will not perform well on the Pentium Pro (due to the use of a
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partial register in the inner loop).
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If you are using an assembler other than GNU as, you will have to
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translate match.S to use your assembler's syntax. (Have fun.)
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Brian Raiter
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breadbox@muppetlabs.com
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April, 1998
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Added for zlib 1.1.3:
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The patches come from
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http://www.muppetlabs.com/~breadbox/software/assembly.html
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To compile zlib with this asm file, copy match.S to the zlib directory
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then do:
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CFLAGS="-O3 -DASMV" ./configure
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make OBJA=match.o
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