Re: [lc-devel] Chunk list issues

[Mauricio L. <mau...@gm...>]

On 6/21/06, Mauricio Lin <mau...@gm...> wrote:
> Hi Gupta,
>
> On 6/21/06, Nitin Gupta <nit...@gm...> wrote:
> > Hi Mauricio,
> >
> > Mauricio Lin wrote:
> > > Regarding the master chunk list (chunks) in the struct chunk, does it
> > > store the chunks of one page cache or several page caches? Will be
> > > there one master chunk list per page cache radix tree?
> >
> > 'master chunk list' is list of all chunks -- these chunks may be part of a file,
> > part of anon page, or free chunks. Its there to easily merge physically adjacent
> > chunks when a chunk is freed.
>
> You mean there will be one master chunk list for several page cache
> radix tree, right?
>
> >
> > >
> > > I also wonder where the chunk list header will be stored. For instance
> > > the list header of task_struct is stored in the tasks field of
> > > init_task, so when an insertion happens in the list of task_struct,
> > > something like that is used:
> > >
> > > list_add_tail(&p->tasks, &init_task.tasks);
> > >
> > > where the first argument is the element to be inserted and the second
> > > argument corresponds the list header of task_struct.
> > > Thus where the list header of chunks will be stored? Any idea?
> > >
> >
> > A compressed page is stored in many chunks. chunk_head->chunk_list is made to
> > point to first of these chunks and these 'related' chunks are linked together
> > using chunk->next
>
> OK, I know about the chunk_list purpose, but chunk_list is not the
> header of master chunk list, since it is not a list_head. What I am
> trying to say is if you want to add something in the master chunk
> list, you have to use a function as list_add_tail() (or similar one in
> include/linux/list.h) and a header list is needed for representing and
> manipulating the master chunk list. If you are going to add something
> in the master chunk list, certainly functions in include/linux/list.h
> need be used. Let's suppose that list_add_tail() function is used to
> insert a chunk in the list, so in this way something like this is
> used:
>
> list_add_tail(&chk->chunks, chunk_list_head);
>
> chk is a instance of struct chunk, where the field "chunks" is used to
> link to the list.
> chunk_list_head is the header of chunk list of type 'list_head'
> (because every list has a header)
>
> Such can be declared and initiliazed as:
> static LIST_HEAD(chunk_list_head);
>
> The chunk_list_head  (header of master chunk list) must be stored in
> some place. So my question is where it is going to be stored ?
>

Perhaps create an init_chunk that stores the header of master chunk
list is a good way. So that follows the same idea of init_task for
list of task_struct.

> BR,
>
> Mauricio Lin.
>