Re: [PATCH 3/3] mm/memcg: apply add/del_page to lruvec

Hi Hugh,
On Sun, May 13, 2012 at 10:02:28PM -0700, Hugh Dickins wrote:

Take lruvec further: pass it instead of zone to add_page_to_lru_list()
and del_page_from_lru_list(); and pagevec_lru_move_fn() pass lruvec
down to its target functions.

This cleanup eliminates a swathe of cruft in memcontrol.c,
including mem_cgroup_lru_add_list(), mem_cgroup_lru_del_list() and
mem_cgroup_lru_move_lists() - which never actually touched the lists.

In their place, mem_cgroup_page_lruvec() to decide the lruvec,
previously a side-effect of add, and mem_cgroup_update_lru_size()
to maintain the lru_size stats.

I have a stupid question. I'm not sure whether there is reduplication
to put both "page" and "zone" parameter in mem_cgroup_page_lruvec(),
for I noticed that the "struct zone *zone" parameter are usually from 
page_zone(page) in most cases. I think that the semantics of this function
is to grab the lruvec the page belongs to. So will it be ok if we pass
only "page" as the parameter, which I think would be cleaner? Please
fix me if I missed something.

Thanks

Baozi

Whilst these are simplifications in their own right, the goal is to
bring the evaluation of lruvec next to the spin_locking of the lrus,
in preparation for a future patch.

Signed-off-by: Hugh Dickins <hughd@google.com>

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