Re: JFFS3 & performance

Artem B. Bityuckiy
2004-12-16T14:27:30Z

On Thu, 16 Dec 2004, Joakim Tjernlund wrote:

> Hi List
>
> I am a long time JFFS2 user(and developer), but I haven't been following
> JFFS2 for a year or two. I have noticed that JFFS3 has begun and I figured
> I would offer a few thoughts.
>
> 1) Consider changing the start seed to crc32 from 0 to -1. Zero
> is not a good start seed for crc32
If you do point 2 this will not be needed :-)

>
> 2) Consider another checksum algorithm. Crc32 is very expensive
> and JFFS2 suffered severely in the early days. Now that crc32 is
> very optimized that problem is less visible, but crc32 is still
> expensive. Maybe an Adler32 checksum is good enough or a crc16?
IMHO, NAND/ECC NOR are additionally protected by ECCs so that sounds
reasonable. NORs are reliable, so that is reasonable too, IMHO.

>
> 3) Don't calculate a Adler32 checksum when comressing with zlib.
> JFFS2 already has its own checksum.
This is really seems reasonable. Personally I didn't do that, but guess it
is possible to ask zlib not to add Adler32 checksums, right?

I'll put your ideas to jffs3/TODO if you don't mind :-)

--
Best Regards,
Artem B. Bityuckiy,
St.-Petersburg, Russia.