JFFS3 & performance

[Joakim Tjernlund]

> On Thu, 16 December 2004 20:15:00 +0100, Jörn Engel wrote:
> >
> > PS: Now you've done it.  I'll implement crc24 and crc16 and benchmark
> > them against adler32.  Darn you!
>
> Testcase going through 45MB of data in chunks of 4k.  Machine is
> PIII-1166 with warm caches.
>
> Doing three runs and discarding the fastest and slowest ones:
>
> crc32:
> real    0m0.214s
> user    0m0.133s
> sys     0m0.076s
>
> adler32:
> real    0m0.128s
> user    0m0.061s
> sys     0m0.066s
>
> crc24:
> real    0m0.969s
> user    0m0.882s
> sys     0m0.073s
>
> crc16:
> real    0m0.382s
> user    0m0.312s
> sys     0m0.061s
>
>
> Looks like those cold hard numbers beat the crap out of my previous
> argument.  So unless someone can seriously optimize below functions,
> just pick adler32.

hmm, crc32 is much faster than crc16/crc24. That means that there is plenty of room
for optimization. One probably needs for find a table driven algoritm and do
a little unrolling.

 Jocke