Re: Linus' sha1 is much faster!

Giuseppe Scrivano wrote:

Hi Pádraig,

I tried to reproduce your results but I wasn't able to do it.  The
biggest difference on a 300MB file I noticed was approximately 15% using
on both implementations -O2, and 5% using -O3.
My GCC version is "gcc (Debian 4.3.3-14) 4.3.3" and the CPU is: Intel(R)
Pentium(R) D CPU 3.20GHz.

I also spent some time trying to improve the gnulib SHA1 implementation
and it seems a lookup table can improve things a bit.

Can you please try the patch that I have attached and tell me which
performance difference (if any) you get?

Thanks for looking at this Giuseppe
and sorry for not mentioning my GCC and CPU.

Note the binaries below is compiled with
$(rpm -q --qf="%{OPTFLAGS}\n" coreutils)
for consistency, which on my F11 machines is:

  -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
  -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i586
  -mtune=generic -fasynchronous-unwind-tables -D_GNU_SOURCE=1

Testing on 2 machines I have here:

$ rpm -q gcc
gcc-4.4.1-2.fc11.i586
$ grep "model name" /proc/cpuinfo | head -n1 | tr -s '[:blank:]' ' '
model name : Intel(R) Pentium(R) M processor 1.70GHz
$ truncate -s300MB sha1.test
$ time sha1sum sha1.test
real    0m3.540s
$ time linus-sha1 sha1.test
real    0m2.319s (-34%)
$ time  giuseppe-sha1sum sha1.test
real    0m3.513s (-.8%)

$ rpm -q gcc
gcc-4.4.1-2.fc11.i586
$ grep "model name" /proc/cpuinfo | head -n1 | tr -s '[:blank:]' ' '
model name : Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz
$ truncate -s300MB sha1.test
$ time sha1sum sha1.test
real    0m1.857s
$ time linus-sha1 sha1.test
real    0m1.102s (-40%)
$ time giuseppe-sha1sum sha1.test
real    0m1.932s (+ 4%)

cheers,
Pádraig.