Re: [PATCH 0/8] zcache: page cache compression support

Pekka Enberg
2011-01-20T13:16:06Z

Hi Christoph,

On Thu, Jan 20, 2011 at 07:33:29AM -0500, Nitin Gupta wrote:
>> I just started looking into kztmem (weird name!) but on
>> the high level it seems so much similar to zcache with some
>> dynamic resizing added (callback for shrinker interface).
>>
>> Now, I'll try rebuilding zcache according to new cleancache
>> API as provided by these set of patches. This will help refresh
>> whatever issues I was having back then with pagecache
>> compression and maybe pick useful bits/directions from
>> new kztmem work.

On Thu, Jan 20, 2011 at 2:47 PM, Christoph Hellwig <hch@infradead.org> wrote:
> Yes, we shouldn't have two drivers doing almost the same in the
> tree.  Also adding core hooks for staging drivers really is against
> the idea of staging of having a separate crap tree.  So it would be
> good to get zcache into a state where we can merge it into the
> proper tree first.  And then we can discuss if adding an abstraction
> layer between it and the core VM really makes sense, and if it does
> how.   But I'm pretty sure there's now need for multiple layers of
> abstraction for something that's relatively core VM functionality.
>
> E.g. the abstraction should involve because of it's users, not the
> compressed caching code should involve because it's needed to present
> a user for otherwise useless code.

I'm not sure which hooks you're referring to but for zcache we did this:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=b3a27d0529c6e5206f1b60f60263e3ecfd0d77cb

I completely agree with getting zcache merged properly before going
for the cleancache stuff.

Pekka