Re: [Yaffs] How to test in linux w/real NAND using userspace…

On Sunday 11 March 2012 06:07:13 Peter Barada wrote:
> Charles e al,
>
> I'm working on adding read-distrub counting to YAFFS (to force a garbage
> collection when the number of reads in a block hit a certain limit (20K
> for MT29C4G48MAZAPAKQ5 OMAP PoP), and I'm looking for a straight-forward
> testing harness that will beat up YAFFS pretty hard.
>
> Googling around didn't come up with much obvious, so I'm asking what to
> use to test YAFFS out-of-kernel (i.e. using a userspace app that mounts
> a partition and thrash it) instead of nandsim and in-kernel testing...
>
> Thanks in advance!

Peter

There are three ways I can think of to achieve this:

Take the simulation code in yaffs direct and write a AND interface that calls
the userspace mtd functions. These are specced in mtd/mtd-user,h

Another way to do this is to work the changes into a hacked version of u-boot
or such.

Yet another way is to stick with Linux. Straight Linux will cache data in the
VFS which will not abuse the read path as you desire. You can ask Linux to
drop the caches by doing:
echo 3 > /proc/sys/vm/drop_caches

Thus something like:

while true; do cat /yaffs/dir/file > /dev/null; done

in parallel with

while true; do sleep 0.1; echo 3 > /proc/sys/vm/drop_caches; done

should do some serious read pounding.

-- Charles