[Yaffs] directory mtime update requires about 30% more I/O i…

Hi,

I run postmark on two versions of yaffs2, one with mtime update and one without,
with a modified nandsim, which records how many read/write/erase during the
test. The result shows that with the mtime update enabled, yaffs2 needs about
30% more read/write/erase I/O in postmark.

In yaffs without mtime update(more clearly, with yaffs_fs.c v1.80 in the cvs
repository, and yaffs_guts.c v1.82) the read/write/erase counting result is:

Read0 195328 ReadOOB 178371 Write0 357501 WriteOOB 0 Erase 3663

In yaffs with mtime update(yaffs_fs.c v1.81 and yaffs_guts.c v1.84), the
counting result is:

Read0 288958 ReadOOB 178371 Write0 451131 WriteOOB 0 Erase 5047

Well, I have have no idea whether this will cause efficiency problems in
realworld applications.

Here are the commands I run in postmark, with a 256MB MTD partition:

set number 10000
set transactions 50000
set subdirectories 1000
set buffering false
set seed 2
run

Karl
2009.6.2