On Wed, Mar 03, 2021 at 01:59:13PM +0800, Muchun Song wrote:
> We know that the unit of slab object charging is bytes, the unit of
> kmem page charging is PAGE_SIZE. If we want to reuse obj_cgroup APIs
> to charge the kmem pages, we should pass PAGE_SIZE (as third parameter)
> to obj_cgroup_charge(). Because the size is already PAGE_SIZE, we can
> skip touch the objcg stock. And obj_cgroup_{un}charge_page() are
> introduced to charge in units of page level.
>
> In the later patch, we also can reuse those two helpers to charge or
> uncharge a number of kernel pages to a object cgroup. This is just
> a code movement without any functional changes.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
This patch looks good to me, even as a standalone refactoring.
Please, rename obj_cgroup_charge_page() to obj_cgroup_charge_pages()
and the same with uncharge. It's because _page suffix usually means
we're dealing with a physical page (e.g. struct page * as an argument),
here it's not the case.
Please, add my Acked-by: Roman Gushchin <guro@xxxxxx>
after the renaming.
Thank you!
> ---
> mm/memcontrol.c | 46 +++++++++++++++++++++++++++++++---------------
> 1 file changed, 31 insertions(+), 15 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 845eec01ef9d..faae16def127 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3056,6 +3056,34 @@ static void memcg_free_cache_id(int id)
> ida_simple_remove(&memcg_cache_ida, id);
> }
>
> +static inline void obj_cgroup_uncharge_page(struct obj_cgroup *objcg,
> + unsigned int nr_pages)
> +{
> + rcu_read_lock();
> + __memcg_kmem_uncharge(obj_cgroup_memcg(objcg), nr_pages);
> + rcu_read_unlock();
> +}
> +
> +static int obj_cgroup_charge_page(struct obj_cgroup *objcg, gfp_t gfp,
> + unsigned int nr_pages)
> +{
> + struct mem_cgroup *memcg;
> + int ret;
> +
> + rcu_read_lock();
> +retry:
> + memcg = obj_cgroup_memcg(objcg);
> + if (unlikely(!css_tryget(&memcg->css)))
> + goto retry;
> + rcu_read_unlock();
> +
> + ret = __memcg_kmem_charge(memcg, gfp, nr_pages);
> +
> + css_put(&memcg->css);
> +
> + return ret;
> +}
> +
> /**
> * __memcg_kmem_charge: charge a number of kernel pages to a memcg
> * @memcg: memory cgroup to charge
> @@ -3180,11 +3208,8 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
> unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT;
> unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);
>
> - if (nr_pages) {
> - rcu_read_lock();
> - __memcg_kmem_uncharge(obj_cgroup_memcg(old), nr_pages);
> - rcu_read_unlock();
> - }
> + if (nr_pages)
> + obj_cgroup_uncharge_page(old, nr_pages);
>
> /*
> * The leftover is flushed to the centralized per-memcg value.
> @@ -3242,7 +3267,6 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
>
> int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
> {
> - struct mem_cgroup *memcg;
> unsigned int nr_pages, nr_bytes;
> int ret;
>
> @@ -3259,24 +3283,16 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
> * refill_obj_stock(), called from this function or
> * independently later.
> */
> - rcu_read_lock();
> -retry:
> - memcg = obj_cgroup_memcg(objcg);
> - if (unlikely(!css_tryget(&memcg->css)))
> - goto retry;
> - rcu_read_unlock();
> -
> nr_pages = size >> PAGE_SHIFT;
> nr_bytes = size & (PAGE_SIZE - 1);
>
> if (nr_bytes)
> nr_pages += 1;
>
> - ret = __memcg_kmem_charge(memcg, gfp, nr_pages);
> + ret = obj_cgroup_charge_page(objcg, gfp, nr_pages);
> if (!ret && nr_bytes)
> refill_obj_stock(objcg, PAGE_SIZE - nr_bytes);
>
> - css_put(&memcg->css);
> return ret;
> }
>
> --
> 2.11.0
>
