Re: small erase block size with EBS

[kevinwu <kevinwu@e28.com>]

Hi Ferenc,
I successfully mounted a 128KiB erase block size summary image on a
16KiB erase block size NAND. The mounting speed is very high. It takes
only about 0.5 second mounting on a 32MiB partition with 90% disk
full.(My cpu is ARM926 running at 201 MHz) It seems OK. The performance
is good. I modified JFFS2 source code a little.
I changed souce code in function jffs2_do_fill_super()
from:
c->sector_size = c->mtd->size;
to:
c->sector_size = 0x00020000; //erase block size of image you generated. 

It does work if the jffs2 partition has no bad block.
If there is a bad block, it will get error imformation. But I will fix
this bug soon. I know what happend. 

在 2005-11-22二的 14:53 +0100，Ferenc Havasi写道：
> Hi,
> 
> > I have a NAND flash with a small erase block(16KiB)
> > When I use sumtool, I find that the summary image size is much larger
> > than the original one if I use option --eraseblock=0x4000.
> > But When I use option --eraseblock=0x20000, The summary image is a bit
> > larger than the original one.
> > EBS fits for large erase block as far as I know. 
> > That is to say, I can not use EBS if the NAND erase block is small. What
> > a pitty!
>  > Is there any way to use EBS on a small erase block size NAND?
> 
> EBS should work on your system but if the erase block size is small it 
> may be not too usefull. Generally if you use bigger erase block size the 
> speedup will be greater and the "used place penalty" will be smaller.
> 
> So I suggest to test it: measure the rete of speedup and the difference 
> in image size on your system, and you can decide it is OK for you or not.
> 
> > What about CS?
> 
> CS doesn't depend on erase block size as EBS does, so you may try it. 
> The code of CS is more then one mouth old, so you should use it with 
> earlier mtd snapshot. If you can wait a little we will update it at the 
> first week of december.
It seems a better choise. I will try it.

Thanks for your information.
-- 
Best Regards

Kevin Wu

System Software Engineer, E28.com


Office: 86-21-23060088-352