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    SubjectRe: [PATCH v4 06/25] memcg: Make it possible to use the stock for more than one page.
    On Mon 18-06-12 14:27:59, Glauber Costa wrote:
    > From: Suleiman Souhlal <ssouhlal@FreeBSD.org>
    >
    > Signed-off-by: Suleiman Souhlal <suleiman@google.com>
    > Signed-off-by: Glauber Costa <glommer@parallels.com>
    > Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    I am not sure the patch is good to merge on its own without the rest.
    One comment bellow.

    > ---
    > mm/memcontrol.c | 18 +++++++++---------
    > 1 file changed, 9 insertions(+), 9 deletions(-)
    >
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index ce15be4..00b9f1e 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    > @@ -1998,19 +1998,19 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
    > static DEFINE_MUTEX(percpu_charge_mutex);
    >
    > /*
    > - * Try to consume stocked charge on this cpu. If success, one page is consumed
    > - * from local stock and true is returned. If the stock is 0 or charges from a
    > - * cgroup which is not current target, returns false. This stock will be
    > - * refilled.
    > + * Try to consume stocked charge on this cpu. If success, nr_pages pages are
    > + * consumed from local stock and true is returned. If the stock is 0 or
    > + * charges from a cgroup which is not current target, returns false.
    > + * This stock will be refilled.
    > */
    > -static bool consume_stock(struct mem_cgroup *memcg)
    > +static bool consume_stock(struct mem_cgroup *memcg, int nr_pages)
    > {
    > struct memcg_stock_pcp *stock;
    > bool ret = true;

    I guess you want:
    if (nr_pages > CHARGE_BATCH)
    return false;

    because you don't want to try to use stock for THP pages.

    >
    > stock = &get_cpu_var(memcg_stock);
    > - if (memcg == stock->cached && stock->nr_pages)
    > - stock->nr_pages--;
    > + if (memcg == stock->cached && stock->nr_pages >= nr_pages)
    > + stock->nr_pages -= nr_pages;
    > else /* need to call res_counter_charge */
    > ret = false;
    > put_cpu_var(memcg_stock);
    > @@ -2309,7 +2309,7 @@ again:
    > VM_BUG_ON(css_is_removed(&memcg->css));
    > if (mem_cgroup_is_root(memcg))
    > goto done;
    > - if (nr_pages == 1 && consume_stock(memcg))
    > + if (consume_stock(memcg, nr_pages))
    > goto done;
    > css_get(&memcg->css);
    > } else {
    > @@ -2334,7 +2334,7 @@ again:
    > rcu_read_unlock();
    > goto done;
    > }
    > - if (nr_pages == 1 && consume_stock(memcg)) {
    > + if (consume_stock(memcg, nr_pages)) {
    > /*
    > * It seems dagerous to access memcg without css_get().
    > * But considering how consume_stok works, it's not
    > --
    > 1.7.10.2
    >
    > --
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    --
    Michal Hocko
    SUSE Labs
    SUSE LINUX s.r.o.
    Lihovarska 1060/12
    190 00 Praha 9
    Czech Republic


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