jffs2 Erase Block Summary overhead

[Matthieu CASTET <matthieu.castet@parrot.fr>]

Hi,

after doing some test on a 64MB nand flash, we see that only 50 MB can 
be stored on the filesystem [1]. The extra 10 MB are taken by jffs2 summary.
If we disable jffs2 sumary in the kernel, the 10MB become available.

Is there a way to reduce this overhead ?
20 % seems really big.

May be Centralized Summary [3] give better result ?
What is its status ?

Matthieu

[1]
# time mount /dev/mtdblock3 -t jffs2 /tmp/mnt/ ; time cat 
/tmp/mnt/root/file.1 > /dev/null ; du -sh /tmp/mnt; df
real    0m 3.05s
user    0m 0.00s
sys     0m 3.05s
real    0m 0.34s
user    0m 0.01s
sys     0m 0.33s
50.6M   /tmp/mnt
Filesystem                Size      Used Available Use% Mounted on
/dev/mtdblock3           61.5M     60.7M    832.0k  99% /tmp/mnt

[2]
# time mount /dev/mtdblock3 -t jffs2 /tmp/mnt/ ; time cat 
/tmp/mnt/root/file.1 > /dev/null ; du -sh /tmp/mnt; df
real    0m 11.30s
user    0m 0.01s
sys     0m 11.28s
real    0m 0.35s
user    0m 0.00s
sys     0m 0.33s
50.6M   /tmp/mnt
/dev/mtdblock3           61.5M     51.2M     10.3M  83% /tmp/mnt

[3]
http://www.inf.u-szeged.hu/jffs2/mount.php