[Yaffs-archive] Re: YAFFS - YAFFS2 starts

[Wookey]

On Mon 04 Nov, Charles Manning wrote:
> I have started working on YAFFS2.

> The main purpose behind YAFFS2 is to support the larger NAND parts with 2kB
> pages and zero rewrite.  But wait, there's more... lower RAM footprint,
> faster,...

> YAFFS2 needs at least a 1kB chunk size. On 512byte pages you can do this by
> just using two pages per chunk. This means a bit more wasted space at the end
> of files. Thus, probably the best approach will be to use YAFFS1 on NAND
> arrays less than, say, 128MB.

> Since almost all the algorithms are the same for YAFFS1 and YAFFS2, I expect
> to keep the code together with YAFFS1 or YAFFS2 being run-time selectable (ie
> as a flag in the device structure).

> Any ideas/input/wishes more than welcome.

> Herewith a brief outline.

Looks good. A few queries presumalby the timings are theoritical at this
stage - did you do profiling on YAFFS1 and then extrapolate to YAFFS2, or
just work them out from the combination of YAFFS behaviour and NAND timing
specs?

What does the 2KB pagesx16 column mean? A chunk size of 2k and a block size
of 32K, or a 32K chunk size with 2K pages?

I don't see why the RAM footprint decreases - is this mostly a side-effect
of the chunk size (and thus the average 'wasted space') growing, and hence
number of chunks to be tracked in memory reducing?

Wookey
-- 
Aleph One Ltd, Bottisham, CAMBRIDGE, CB5 9BA, UK  Tel +44 (0) 1223 811679
work: http://www.aleph1.co.uk/     play: http://www.chaos.org.uk/~wookey/


---------------------------------------------------------------------------------------
This mailing list is hosted by Toby Churchill open software (www.toby-churchill.org).
If mailing list membership is no longer wanted you can remove yourself from the list by 
sending an email to yaffs-request@toby-churchill.org with the text "unsubscribe" 
(without the quotes) as the subject.