[OLPC-devel] Re: [linux-mm-cc] Weekly work summary [7/12]

[Anderson Briglia]

Hi Nitin,

On 7/16/06, Nitin Gupta <nitingupta.mail at gmail.com> wrote:
> I'm having a _very_ hard time fixing all things related to vswap.
> Especially, storing and restoring pages that have multiple PTEs pointing
> to them. Many code paths assume there must be block device associated
> with a swap and they OOPS when they deal with vswap. Also, there's a
> problem that vswap once full, can't be reused. Fixing this is taking so
> much time (and is not yet fixed).
>
> So, where is project now?
> -- Working on to make storing and restoring anon pages to/from vswap
> stable. This is base of ccaching for anon pages.

Vswap simulates a real swap area, right? I still have a doubt: If I
have a compressed page spreaded in some chunks, this page should be
regrouped to go to a swap area (real or virtual), and the page can be
stored at compressed form or not. How about vswap? AFAIK, vswap is
used just for anon pages (until now), but the pages are transfered
in/out vswap using the same swap mechanism (shrink_list() and
pageout()). What I'm not understanding is how vswap will act as a
ccache if the chunks will not use the vswap, just regrouped compressed
pages. I thought that the chunk lists (free and used) are the
compressed cache because the pages will be stored there before going
to a swap area (real or virtual), is this right?

Sorry if I'm a little bit confusing, but I'm trying to understand your
approach. :)

Best regards,

Anderson Briglia