Re: Substituting Checksum Algorithm (was: Enabling Checksums)

On 4/26/13 3:57 PM, Jeff Davis wrote:
> The second patch adds the configure-time check for the right
> compilation flags, and uses them when compiling checksum.c. I
> called the new variable CFLAGS_EXTRA, for lack of a better idea,
> so feel free to come up with a new name. It doesn't check for, or
> use, -msse4.1, but that can be specified by the user by
> configuring with CFLAGS_EXTRA="-msse4.1".

Thank you, that is the last piece I was looking at but couldn't nail 
down on my own.  With that I should be able to duplicate both the 
slicing by 8 CRC speedup Ants sent over (which also expected some 
optimization changes) and trying something FNV based this weekend.

I think I need to do two baselines:  master without checksums, and 
master with extra optimizations but still without checksums.  It may be 
the case that using better compile time optimizations gives a general 
speedup that's worth considering regardless.  The optimizations seem to 
have a very significant impact on the checksum feature, but I'd like to 
quantify how they change the code a little bit before even getting into 
that.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
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