On Thu 09-08-12 17:01:09, Glauber Costa wrote:
> From: Suleiman Souhlal <ssouhlal@xxxxxxxxxxx>
>
> We currently have a percpu stock cache scheme that charges one page at a
> time from memcg->res, the user counter. When the kernel memory
> controller comes into play, we'll need to charge more than that.
>
> This is because kernel memory allocations will also draw from the user
> counter, and can be bigger than a single page, as it is the case with
> the stack (usually 2 pages) or some higher order slabs.
>
> [ glommer@xxxxxxxxxxxxx: added a changelog ]
>
> Signed-off-by: Suleiman Souhlal <suleiman@xxxxxxxxxx>
> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/memcontrol.c | 28 ++++++++++++++++++----------
> 1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 95162c9..bc7bfa7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2096,20 +2096,28 @@ struct memcg_stock_pcp {
> 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.
> +/**
> + * consume_stock: Try to consume stocked charge on this cpu.
> + * @memcg: memcg to consume from.
> + * @nr_pages: how many pages to charge.
> + *
> + * The charges will only happen if @memcg matches the current cpu's memcg
> + * stock, and at least @nr_pages are available in that stock. Failure to
> + * service an allocation will refill the stock.
> + *
> + * returns true if succesfull, false otherwise.
> */
> -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;
>
> + if (nr_pages > CHARGE_BATCH)
> + return false;
> +
> 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);
> @@ -2408,7 +2416,7 @@ 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 {
> @@ -2433,7 +2441,7 @@ 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
> --
> 1.7.11.2
>
> --
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--
Michal Hocko
SUSE Labs
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