Re: [RFC] Structure in Compressed Cache

[Marcelo Tosatti <marcelo@conectiva.com.br>]

On Mon, 30 Oct 2000, Rodrigo S. de Castro wrote:

> Hello,
> 
> 	In my implementation of compressed cache (kernel 2.2.16), I
> started the project having my cache as a slab cache, structure
> provided by kernel. I have all step 1 (a cache with no compression)
> done, but I had a problem with marking pages in my cache. After an
> email sent to the list about this subject, I started looking at shared
> memory mechanism (mainly ipc/shm.c), and I saw that there's another
> way of making it: with a page table allocation and memory mapping. I
> could go on with my initial idea (with slab cache) but I think that
> doing the latter way (with page table and memory mapping) would be
> more complete (and, of course, harder). I will have a pool of
> (compressed) pages that gotta be always in memory and will be
> "between" physical memory and swap. As the project is growing I would
> like to define now which path to follow, taking in account
> completeness and upgradeability (to future versions of kernel). Which
> way do you think that is better? Please, I also ask you to tell me in
> case you know if there's another way, maybe better, of doing it.

Slab cache memory is physically contiguous and non swappable, so it may be
a waste to use it to cache userspace data. 

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