jffs2 Erase Block Summary overhead

[Matthieu CASTET]

Hi,

David Woodhouse a écrit :
> 
> There's a lot of redundant information in the summary; I think we could
> halve it fairly easily.
That would be great :)

> I don't believe your 20% figure though -- that's
> too high. You really can't rely on the output of df.
> 
But the jffs2 layer say "no space left on device", so the it is really full.

For more information on the test procedure, I fill the jffs2 filesystem 
with someting like :
"i=0; while true; do dd if=/dev/urandom of=file.$i count=1024; 
i=$(($i+1));done"
And I can create only 93 complete files, a incomplete file of 430 KB 
(and there should be 4 MB taken file others files).


May be I am on a worse test case ?

If I remove "Erase Block Summary", I can really fill the jffs2 up to 
60MB [1] instead of 51MB.

Thanks,

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 11.91s
user    0m 0.00s
sys     0m 11.91s
real    0m 0.36s
user    0m 0.01s
sys     0m 0.35s
59.8M   /tmp/mnt
Filesystem                Size      Used Available Use% Mounted on
/dev/ram0                 4.4M      4.4M         0 100% /
none                      7.0M     16.0k      7.0M   0% /tmp
none                      7.0M     16.0k      7.0M   0% /tmp
tmpfs                     7.0M     16.0k      7.0M   0% /tmp
/dev/mtdblock3           61.5M     60.9M    640.0k  99% /tmp/mnt