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    SubjectRe: [patch 10/11] mm: make per-memcg LRU lists exclusive
    On Mon 12-09-11 12:57:27, Johannes Weiner wrote:
    > Now that all code that operated on global per-zone LRU lists is
    > converted to operate on per-memory cgroup LRU lists instead, there is
    > no reason to keep the double-LRU scheme around any longer.
    >
    > The pc->lru member is removed and page->lru is linked directly to the
    > per-memory cgroup LRU lists, which removes two pointers from a
    > descriptor that exists for every page frame in the system.
    >
    > Signed-off-by: Johannes Weiner <jweiner@redhat.com>
    > Signed-off-by: Hugh Dickins <hughd@google.com>
    > Signed-off-by: Ying Han <yinghan@google.com>

    Reviewed-by: Michal Hocko <mhocko@suse.cz>

    Minor comments/questions bellow.
    > ---
    > include/linux/memcontrol.h | 54 +++-----
    > include/linux/mm_inline.h | 21 +--
    > include/linux/page_cgroup.h | 1 -
    > mm/memcontrol.c | 319 ++++++++++++++++++++-----------------------
    > mm/page_cgroup.c | 1 -
    > mm/swap.c | 23 ++-
    > mm/vmscan.c | 81 +++++-------
    > 7 files changed, 228 insertions(+), 272 deletions(-)
    >
    [...]
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index 465001c..a7d14a5 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    [...]
    > @@ -934,115 +954,123 @@ EXPORT_SYMBOL(mem_cgroup_count_vm_event);
    > * When moving account, the page is not on LRU. It's isolated.
    > */
    >
    > -struct page *mem_cgroup_lru_to_page(struct zone *zone, struct mem_cgroup *mem,
    > - enum lru_list lru)
    > +/**
    > + * mem_cgroup_lru_add_list - account for adding an lru page and return lruvec
    > + * @zone: zone of the page
    > + * @page: the page
    > + * @lru: current lru
    > + *
    > + * This function accounts for @page being added to @lru, and returns
    > + * the lruvec for the given @zone and the memcg @page is charged to.
    > + *
    > + * The callsite is then responsible for physically linking the page to
    > + * the returned lruvec->lists[@lru].
    > + */
    > +struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
    > + enum lru_list lru)

    I know that names are alway tricky but what about mem_cgroup_acct_lru_add?
    Analogously for mem_cgroup_lru_del_list, mem_cgroup_lru_del and
    mem_cgroup_lru_move_lists.

    [...]
    > @@ -3615,11 +3593,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
    > static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
    > int node, int zid, enum lru_list lru)
    > {
    > - struct zone *zone;
    > struct mem_cgroup_per_zone *mz;
    > - struct page_cgroup *pc, *busy;
    > unsigned long flags, loop;
    > struct list_head *list;
    > + struct page *busy;
    > + struct zone *zone;

    Any specific reason to move zone declaration down here? Not that it
    matters much. Just curious.

    > int ret = 0;
    >
    > zone = &NODE_DATA(node)->node_zones[zid];
    > @@ -3639,16 +3618,16 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
    > spin_unlock_irqrestore(&zone->lru_lock, flags);
    > break;
    > }
    > - pc = list_entry(list->prev, struct page_cgroup, lru);
    > - if (busy == pc) {
    > - list_move(&pc->lru, list);
    > + page = list_entry(list->prev, struct page, lru);
    > + if (busy == page) {
    > + list_move(&page->lru, list);
    > busy = NULL;
    > spin_unlock_irqrestore(&zone->lru_lock, flags);
    > continue;
    > }
    > spin_unlock_irqrestore(&zone->lru_lock, flags);
    >
    > - page = lookup_cgroup_page(pc);
    > + pc = lookup_page_cgroup(page);

    lookup_page_cgroup might return NULL so we probably want BUG_ON(!pc)
    here. We are not very consistent about checking the return value,
    though.

    --
    Michal Hocko
    SUSE Labs
    SUSE LINUX s.r.o.
    Lihovarska 1060/12
    190 00 Praha 9
    Czech Republic


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