[Yaffs] Re: Getting the most out of YAFFS

[Wookey]

+++ Kent Ryhorchuk [06-01-14 14:14 -0800]:
> Hi all,
> 
> I've got it working on a 2GB Samsung NAND flash. 

> There are two big problems I am working on solving:
> 
> 1. Mount time - by ripping out all the MTD code and
> really optimizing the driver I've got the mount time
> down to a minute. The time budget os 10s to cold-boot
> the entire system. Uh-oh.

Smaller partitions has already been mentioned. The other approach to
speeding up boot is checkpointing. The underlying problem is that because
yaffs is log-structured it needs to scan the whole partition (or at least
all the oobs) to reconstruct the ram data structures. Assuming you normally
have neat shutdowns (rather than hard power-offs) then recording the data
structure on shutdown can save a lot of scan time on restart.

There are also techniques for doing 'intermediate checkpoints' to speed
things up even on an untidy shutdown, but that is more work.

We have already looked into implementing this and I think Charles has a
reasonable plan of how togo about it, but no-one has stumped up the cash, or
volunteered to do it themselvers, to actually make it happen yet.

Wookey
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