Re: [lc-devel] Chunk list issues

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

Hi Gupta,

BTW, is there any special reason the related chunks are just
singly-linked list? Could they be also doubly-linked list as the
master chunk list?

BR,

Mauricio Lin.

On 6/21/06, Mauricio Lin <mau...@gm...> wrote:
> Hi Gupta,
>
> I started to implement some basic operations related to chunk list
> (not finished yet). Take a look if such functions and macros can be
> useful.
>
> /* This works as the header of master chunk list*/
> struct chunk init_chunk = {
>         .start_addr = NULL,
>         .size = 0,
>         .next = NULL,
>         .chunks = LIST_HEAD_INIT(init_chunk.chunks)
> };
>
> #define next_chunk(chk) list_entry((chk)->chunks.next, struct chunk, chunks)
>
> #define prev_chunk(chk) list_entry((chk)->chunks.prev, struct chunk, chunks)
>
> #define for_each_chunk(chk) \
>         for (chk = &init_chunk ; (chk = next_chunk(chk)) != &init_chunk ; )
>
> static inline void add_chunk_to_list(struct chunk *chk)
> {
>         list_add_tail(&chk->chunks, &init_chunk.chunks);
> }
>
> static inline void del_chunk_from_list(struct chunk *chk)
> {
>         list_del(&chk->chunks);
> }
>
> What do you think?
>
> BR,
>
> Mauricio Lin.
>
>
> On 6/21/06, Nitin Gupta <nit...@gm...> wrote:
> > Hi Mauricio,
> >
> > Mauricio Lin wrote:
> > > On 6/21/06, Nitin Gupta <nit...@gm...> wrote:
> > >> 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?
> > >
> >
> > Yes.
> > In other words: nodes of several page cache radix trees will be replaces by
> > chunk_head's. These chunk_head's point to corres. list of chunks. And all these
> > chunks are linked together by master chunk list (MCL).
> >
> > >>
> > >> >
> > >> > 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 ?
> > >
> >
> > I was still stuck with 'related chunk list' (ok, RCL) while answering you :)
> > All these lists: MCL, LRU_{page_cache_clean,page_cache_dirty,anon},
> > Free_{good,bad,ugly} will have their heads as globals in mm/ccache.c
> >
> > Of these:
> > MCL lists use chunk->chunks (doubly linked)
> > LRU lists use chunk_head->lru (doubly linked)
> > Free lists use chunk->next (singly linked)
> >
> >
> > Cheers,
> > Nitin Gupta
> >
> >
> >
>