about the _dtype_ parameter

[xiaochuanxv at gmail.com]

Hi,

On Tue, 2009-01-13 at 11:41 +0200, Artem Bityutskiy wrote:
> 
> Tried the latest ubifs-2.6 tree and @dtype is always UBI_UNKNOWN (3).
> This is also strange though, I'll look at this.

Unfortunately, if the @dtype is always UBI_UNKNOWN, this result in a
great increase in the physical erase-block erasures due to wear-leveling
processes.

(Suppose wr-ratio represent the ratio of erasures due to wear-leveling
to erasure total physical erase-block erasures. )
I found that when most of the @dtype is equal to UBI_SHORTTERM, the
wr-ratio is approximately equal to 0.1%, whereas is greater than 4% when
@dtype is always UBI_UNKNOWN. It seem that the data type call-back
policy does NOT make any sense in the current implementation.

FYI, An simple way is of making all data type UBI_SHORTTERM only,
although a bit of data are long term data. Go further and say, @dtype
can be got rid off from UBI clients (e.g., UBIFS), or classifying the
data type as TWO type(UBI_SHORTTERM and UBI_LOANGTERM).


-- 
Best regards,
Xiaochuan Xu (许小川)