Unmapped buffers: to be merged in several days

[Konstantin Belousov]

On Tue, Mar 12, 2013 at 01:04:25AM +0400, Lev Serebryakov wrote:
> Hello, Konstantin.
> You wrote 11 марта 2013 г., 22:24:54:
> 
> KB> If the class does need to access the bio data, to be marked
> KB> unmapped-processing, the class should be rewritten. Now, the class
> KB> should verify is the bio passed is mapped or not, and process the pages
> KB> passed in the bio_ma array instead of bio_data. The involved example is
> KB> sys/dev/md/md.c.
>  Will GEOM class, which needs to touch data (like raid3 or my off-tree
> raid5), benefit from conversion, compare to generic mechanism,
> provided for not-converted by your patch?

First, what do you mean by 'benefit'. Answer would obviously depend
on the criteria.

Second, I do not think that any wizard can usefully answer this question,
for usual criteria like speed or code maintanability.

FWIW, I tried to get an Intel documentation for IOAT engine which should
allow to perform the XOR checksumming of the unmapped buffers, suitable
for e.g. hardware-assisted software raid5, but did not succeeded.
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