How much RAM does JFFS2 use?

[Ricard Wanderlof]

Hi,

I've been running some tests with jffs2/mtd vs ubifs/UBI/mtd. One 
surprising thing was that when the root file system is ubifs, located in 
an UBI volume (although I don't think the latter makes a difference), 
there is much more available RAM as seen by the (busybox) free command.

The root file system is about 26 MB in size (26 MB if ubifs, almost 28 NB 
if jffs2), and contains the same files in both cases. The difference in 
free RAM space is stunning, about 32 MB.

I know jffs2 builds tables in RAM when it scans the device upon mount, but 
I wouldn't expect that much memory to be used.

Now, I'll probably find the culprit as soon as I send this off :-), but at 
the moment of writing I can't think of any other difference between the 
two setups. I'm using the same source tree to build the ubifs and jffs2 
images, and the only difference in the kernel is the compiled-in kernel 
command line specifying which partition to boot from.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30