Re: Reiser4 documentation & specifically current status of repacker, compression, and semantics

[Edward Shishkin <edward@namesys.com>]

Edward Shishkin wrote:

> Hans Reiser wrote:
>
>>  Particularly, define whether large
>> files that cannot be compressed get stored using extents and everything
>> else that regular files use.
>>
>>  
>>
>
> Currently files powered by cryptcompress file plugin have its data 
> stored only in the
> items of CTAIL_ID
>
>> Also, I thought we convert at first flush time, not at every flush
>> time.  Did you write it to check at every flush?
>
>
> no, just turning off and no anymore check, but it can be easily changed
>
>> Not entirely sure we
>> want to do that for large multimedia files that are compressed by
>> hardware, it could add a bunch of CPU, and I would think it would be
>> more complex code, because now you have to convert extents, etc.
>>
>
> Yes, such converting seems to be a complicated workaround. We will need
> something like "clustered extents"
>

So having such "cextents" instead of incompressible ctails on leaf level
will reduce (/=2 times) memory usage and response to emergency flush
(currently there are no any chances for cryptcompress files to be 
eflushed).

Edward.