Charles,
> Can you also post details of the tests you used?
The tests were very simple.
The "write big file" thing stands for { dd if=/dev/urandom
of=/mnt/bigfile bs=512 count=10240 && sync }, the "write folder" thing
is {cp -a /bin /mnt && sync }.
The reason why I started that was the letter from one guy to YAFFS2
list saying that the r/w performance of JFFS2 is higher than that of
YAFFS2... which was contrary to my expectations.
> I find it hard to understand why there should be such a difference in the
> write speed (JFFS2 is 2x YAFFS2) because, apart form gc effects, they should
> both be writing pretty much the same amount to flash and doing equal amounts
> of processing (assuming there is no compression, as you have said).
Yea, I was surprised with that as well, However, after some
considerations, I'm close to the conclusion that it's
controller-specific. The thing is that the OOB is spread across the
page IOT facilitate HW ECC, so it's (512b data, 16b OOB) x 4 actually
for each page, so each OOB write is costly. However, such things
appear more and more as manufacturers go producing cheaper chips that
need stronger ECC.
> I would expect YAFFS2 to grind a bit if you're writing to a partition that has
> just had a lot of files deleted. Since YAFFS2 defers the garbage collection
> until subsequent writes, this impacts on write speed. However that effect
> should not last long.
I haven't had enought time to continue with that, but YAFFS2 writes'
time looks stabler than that of JFFS2 prolly b/c of absense of the
separate GC thread ...
Vitaly
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