Re: JFFS3 & performance

Jörn Engel
2004-12-22T15:56:30Z

On Wed, 22 December 2004 16:30:20 +0100, Joakim Tjernlund wrote:
>
> Can you do
> 1) First run a forward and then a backward version on memory space >= 2*L1 cache
> 2) Then do two forward runs on the same memory.
>
> Compare the delta between 1) and 2)
> That should give a clue if it is worth having a backward version.

In my private not-too-scientific hash-table test, I do a strlen()
before calling engel32. The reverse version is 1.5% faster, even
though the strings are in the 80byte arena. That's well over noise
level.

> > Adler32 beats the hell out of every other algorithm. Except for the
> > backwards part, it appears to be a clear winner.
>
> Have you look at the assembler Engler32 generates? Every instruction counts
> in such small loops.

Not yet. Might be worth a try, though. Since it's losing in direct
comparison, but equal in the hash test, it might be slightly stronger
than adler32.

BTW: I reject the name "Engler32". Few names are worse than
"engel32", but that one is. ;)

Jörn

--
A defeated army first battles and then seeks victory.
-- Sun Tzu