On 27/11/11 01:08, Dave Budenberg wrote:
> (I note that the guidance at http://www.yaffs.net/yaffs-memory-footprint
> seems significantly different from what we are seeing.)
That calculation is for the old YAFFS1 code.
I made a worked example for YAFFS2 on eCos a couple of years ago, based
on updated information provided by Charles at the time. The result can
be seen at
http://www.ecoscentric.com/ecospro/doc/html/ref/yaffs-mem-reqs.html .
> 1. Is what I am seeing appropriate for the configuration we are using?
> 2. Is it realistic to achieve 50kB code size & around 10kB RAM using Yaffs?
I haven't looked into the code size recently, but that sort of RAM
footprint will only be possible with a very small number of files.
If you're using YAFFS2, you may be able to squeeze the code size a bit
by conditioning out the code specific to YAFFS1.
> 3. If Yaffs can’t meet our resource requirements, what alternative file
> systems might be appropriate?
YAFFS is designed for raw NAND, but an SD card is several steps removed
from that and intended to be used by a regular desktop filesystem (vfat,
ext2, etc). Provided you trust that your SD card has a good flash
translation layer providing wear levelling, one of the desktop
journalling filesystems might be worth looking into - though I fear that
that many will have similarly onerous RAM requirements.
Ross
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