[Yaffs] Re: yaffs2 status

[Sergei Sharonov]

Hi,
> > Can anybody post any reference numbers? For example it takes me 20+
> > minutes to mount 256 MByte NAND partion with a 200 MByte file on it
> > when using jffs2.
> 
> That does sound remarkably slow. But obviously it does depend a lot of the
> hardware speed - what is the platform?

at91rm9200 (arm9 @ 180 MHz)
Clarification:
mount returns after 1.5 minutes but then any (first) write or even ls 
takes 10..20 minutes. AFAIK a lot of work is left for gc thread after 
mount is done. I've also seen much worse numbers when the large file 
was saved via ftp. Node size? I have not investigated.


> Some ballpark figures reckon YAFFS(1) is 4 times as fast to boot per MB of
> flash, or twice as fast per meg of data (assuming the JFFS2 FS is
> compressed at 2:1, which is farily typical). (from
> http://www.aleph1.co.uk/talks/yaffs/mgp00025.html which came from collated
> posts to this list).

Hmm.. 8s/77MB seconds in yaffs case and 20m/200MB in jffs2 case is 
more then 4X  ;-)
 
> YAFFS2 is up to twice as fast on read (with 2K pages and 16bit bus) - 
> on 512byte
> pages and 8 bit bus it is same speed as YAFFS1.

That is good to know. I have a 100 Mb/s Ethernet and I need to be able 
to dump log data as fast as possible.

> ecc checking can really slow things down if it is done in software not
> hardware - although that's primarily on writing, so not important for
> initial scan time. 

No hardware ECC here, but one would think 180 MIPS should mitigate that.

> The best way to get some reliable numbers would of course be to try it - it
> should definately be at least twice as fast. We'd be interested to hear what
> you find.

I definetly would like to try yaffs2 out. Where can I find howto?

> Ulitimately the solution to the problem that all log-structured 
> filesystems have
> to scan the whole media on boot, and this takes time is checkpointing
> (storing intermediate, or shutdown, status), and smarter partitioning so 
> you
> can start before scanning the whole media. The latter is available today -
> the former needs sponsoring.

Cannot do much with partitioning since must be able to suck the data out
fast even immediatelly after reset.

Sergei Sharonov