Re: [PATCH 2/3] memcg: unify slab and other kmem pages charging

From: Johannes Weiner
Date: Fri Oct 16 2015 - 20:20:23 EST


Hi Vladimir,

I'm late, but fwiw these patches are great simplifications. Thanks!

One nit below:

On Mon, Oct 05, 2015 at 01:21:42AM +0300, Vladimir Davydov wrote:
> @@ -2404,36 +2376,59 @@ void __memcg_kmem_put_cache(struct kmem_cache *cachep)
> css_put(&cachep->memcg_params.memcg->css);
> }
>
> -int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
> +/*
> + * If @memcg != NULL, charge to @memcg, otherwise charge to the memcg the
> + * current task belongs to.
> + */
> +int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order,
> + struct mem_cgroup *memcg)
> {
> - struct mem_cgroup *memcg;
> - int ret;
> -
> - memcg = get_mem_cgroup_from_mm(current->mm);
> + struct page_counter *counter;
> + unsigned int nr_pages = 1 << order;
> + bool put = false;
> + int ret = 0;
>
> - if (!memcg_kmem_is_active(memcg)) {
> - css_put(&memcg->css);
> - return 0;
> + if (!memcg) {
> + memcg = get_mem_cgroup_from_mm(current->mm);
> + put = true;

I think it'd be better to have an outer function than a magic
parameter for the memcg lookup. Could we fold this in there?

---

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/memcontrol.h | 7 ++++---
mm/memcontrol.c | 36 ++++++++++++++++++------------------
mm/slab.h | 4 ++--
3 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 47677ac..730a65d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -756,8 +756,9 @@ static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
* conditions, but because they are pretty simple, they are expected to be
* fast.
*/
-int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order,
- struct mem_cgroup *memcg);
+int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
+ struct mem_cgroup *memcg);
+int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order);
void __memcg_kmem_uncharge(struct page *page, int order);

/*
@@ -797,7 +798,7 @@ static __always_inline int memcg_kmem_charge(struct page *page,
{
if (__memcg_kmem_bypass(gfp))
return 0;
- return __memcg_kmem_charge(page, gfp, order, NULL);
+ return __memcg_kmem_charge(page, gfp, order);
}

/**
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 15db655..6fc9959 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2378,39 +2378,39 @@ void __memcg_kmem_put_cache(struct kmem_cache *cachep)
css_put(&cachep->memcg_params.memcg->css);
}

-/*
- * If @memcg != NULL, charge to @memcg, otherwise charge to the memcg the
- * current task belongs to.
- */
-int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order,
- struct mem_cgroup *memcg)
+int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
+ struct mem_cgroup *memcg)
{
- struct page_counter *counter;
unsigned int nr_pages = 1 << order;
- bool put = false;
+ struct page_counter *counter;
int ret = 0;

- if (!memcg) {
- memcg = get_mem_cgroup_from_mm(current->mm);
- put = true;
- }
if (!memcg_kmem_is_active(memcg))
- goto out;
+ return 0;

ret = page_counter_try_charge(&memcg->kmem, nr_pages, &counter);
if (ret)
- goto out;
+ return ret;

ret = try_charge(memcg, gfp, nr_pages);
if (ret) {
page_counter_uncharge(&memcg->kmem, nr_pages);
- goto out;
+ return ret;
}

page->mem_cgroup = memcg;
-out:
- if (put)
- css_put(&memcg->css);
+
+ return 0;
+}
+
+int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
+{
+ struct mem_cgroup *memcg;
+ int ret;
+
+ memcg = get_mem_cgroup_from_mm(current->mm);
+ ret = __memcg_kmem_charge_memcg(page, gfp, order, memcg);
+ css_put(&memcg->css);
return ret;
}

diff --git a/mm/slab.h b/mm/slab.h
index 3d667a4..27492eb 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -244,8 +244,8 @@ static __always_inline int memcg_charge_slab(struct page *page,
return 0;
if (is_root_cache(s))
return 0;
- return __memcg_kmem_charge(page, gfp, order,
- s->memcg_params.memcg);
+ return __memcg_kmem_charge_memcg(page, gfp, order,
+ s->memcg_params.memcg);
}

extern void slab_init_memcg_params(struct kmem_cache *);
--
2.6.1
--
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