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Date: Thu, 23 Apr 2020 13:20:06 -0700
From: Roman Gushchin <guro@...com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>, <linux-mm@...ck.org>,
<kernel-team@...com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 07/19] mm: memcg/slab: allocate obj_cgroups for
non-root slab pages
On Wed, Apr 22, 2020 at 01:46:56PM -0700, Roman Gushchin wrote:
> Allocate and release memory to store obj_cgroup pointers for each
> non-root slab page. Reuse page->mem_cgroup pointer to store a pointer
> to the allocated space.
>
> To distinguish between obj_cgroups and memcg pointers in case
> when it's not obvious which one is used (as in page_cgroup_ino()),
> let's always set the lowest bit in the obj_cgroup case.
>
> Signed-off-by: Roman Gushchin <guro@...com>
> ---
> include/linux/mm_types.h | 5 ++++-
> include/linux/slab_def.h | 5 +++++
> include/linux/slub_def.h | 2 ++
> mm/memcontrol.c | 17 +++++++++++---
> mm/slab.c | 3 ++-
> mm/slab.h | 48 ++++++++++++++++++++++++++++++++++++++++
> mm/slub.c | 5 +++++
> 7 files changed, 80 insertions(+), 5 deletions(-)
>
...
> diff --git a/mm/slub.c b/mm/slub.c
> index 8d16babe1829..68c2c45dfac1 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -5992,4 +5992,9 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer,
> {
> return -EIO;
> }
> +
> +int objs_per_slab(struct kmem_cache *cache)
> +{
> + return oo_objects(cache->oo);
> +}
> #endif /* CONFIG_SLUB_DEBUG */
> --
> 2.25.3
>
Ooops, the build bot found that objs_per_slab() was accidentally guarded by
CONFIG_SLUB_DEBUG. An updated version below.
--
>From 6b358e0157815535c3a73b4ce7b28f9c4c7804b3 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@...com>
Date: Wed, 10 Jul 2019 15:44:38 -0700
Subject: [PATCH v3.1 07/19] mm: memcg/slab: allocate obj_cgroups for non-root
slab pages
Allocate and release memory to store obj_cgroup pointers for each
non-root slab page. Reuse page->mem_cgroup pointer to store a pointer
to the allocated space.
To distinguish between obj_cgroups and memcg pointers in case
when it's not obvious which one is used (as in page_cgroup_ino()),
let's always set the lowest bit in the obj_cgroup case.
Signed-off-by: Roman Gushchin <guro@...com>
---
include/linux/mm_types.h | 5 ++++-
include/linux/slab_def.h | 5 +++++
include/linux/slub_def.h | 2 ++
mm/memcontrol.c | 17 +++++++++++---
mm/slab.c | 3 ++-
mm/slab.h | 48 ++++++++++++++++++++++++++++++++++++++++
mm/slub.c | 5 +++++
7 files changed, 80 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 4aba6c0c2ba8..0ad7e700f26d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -198,7 +198,10 @@ struct page {
atomic_t _refcount;
#ifdef CONFIG_MEMCG
- struct mem_cgroup *mem_cgroup;
+ union {
+ struct mem_cgroup *mem_cgroup;
+ struct obj_cgroup **obj_cgroups;
+ };
#endif
/*
diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index abc7de77b988..967a9a525eab 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -114,4 +114,9 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,
return reciprocal_divide(offset, cache->reciprocal_buffer_size);
}
+static inline int objs_per_slab(const struct kmem_cache *cache)
+{
+ return cache->num;
+}
+
#endif /* _LINUX_SLAB_DEF_H */
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 200ea292f250..cbda7d55796a 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -191,4 +191,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,
cache->reciprocal_size);
}
+extern int objs_per_slab(struct kmem_cache *cache);
+
#endif /* _LINUX_SLUB_DEF_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7f87a0eeafec..63826e460b3f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -549,10 +549,21 @@ ino_t page_cgroup_ino(struct page *page)
unsigned long ino = 0;
rcu_read_lock();
- if (PageSlab(page) && !PageTail(page))
+ if (PageSlab(page) && !PageTail(page)) {
memcg = memcg_from_slab_page(page);
- else
- memcg = READ_ONCE(page->mem_cgroup);
+ } else {
+ memcg = page->mem_cgroup;
+
+ /*
+ * The lowest bit set means that memcg isn't a valid
+ * memcg pointer, but a obj_cgroups pointer.
+ * In this case the page is shared and doesn't belong
+ * to any specific memory cgroup.
+ */
+ if ((unsigned long) memcg & 0x1UL)
+ memcg = NULL;
+ }
+
while (memcg && !(memcg->css.flags & CSS_ONLINE))
memcg = parent_mem_cgroup(memcg);
if (memcg)
diff --git a/mm/slab.c b/mm/slab.c
index 9350062ffc1a..f2d67984595b 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1370,7 +1370,8 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
return NULL;
}
- if (charge_slab_page(page, flags, cachep->gfporder, cachep)) {
+ if (charge_slab_page(page, flags, cachep->gfporder, cachep,
+ cachep->num)) {
__free_pages(page, cachep->gfporder);
return NULL;
}
diff --git a/mm/slab.h b/mm/slab.h
index 8a574d9361c1..44def57f050e 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -319,6 +319,18 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
return s->memcg_params.root_cache;
}
+static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
+{
+ /*
+ * page->mem_cgroup and page->obj_cgroups are sharing the same
+ * space. To distinguish between them in case we don't know for sure
+ * that the page is a slab page (e.g. page_cgroup_ino()), let's
+ * always set the lowest bit of obj_cgroups.
+ */
+ return (struct obj_cgroup **)
+ ((unsigned long)page->obj_cgroups & ~0x1UL);
+}
+
/*
* Expects a pointer to a slab page. Please note, that PageSlab() check
* isn't sufficient, as it returns true also for tail compound slab pages,
@@ -406,6 +418,25 @@ static __always_inline void memcg_uncharge_slab(struct page *page, int order,
percpu_ref_put_many(&s->memcg_params.refcnt, nr_pages);
}
+static inline int memcg_alloc_page_obj_cgroups(struct page *page, gfp_t gfp,
+ unsigned int objects)
+{
+ void *vec;
+
+ vec = kcalloc(objects, sizeof(struct obj_cgroup *), gfp);
+ if (!vec)
+ return -ENOMEM;
+
+ page->obj_cgroups = (struct obj_cgroup **) ((unsigned long)vec | 0x1UL);
+ return 0;
+}
+
+static inline void memcg_free_page_obj_cgroups(struct page *page)
+{
+ kfree(page_obj_cgroups(page));
+ page->obj_cgroups = NULL;
+}
+
extern void slab_init_memcg_params(struct kmem_cache *);
extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
@@ -455,6 +486,16 @@ static inline void memcg_uncharge_slab(struct page *page, int order,
{
}
+static inline int memcg_alloc_page_obj_cgroups(struct page *page, gfp_t gfp,
+ unsigned int objects)
+{
+ return 0;
+}
+
+static inline void memcg_free_page_obj_cgroups(struct page *page)
+{
+}
+
static inline void slab_init_memcg_params(struct kmem_cache *s)
{
}
@@ -481,12 +522,18 @@ static __always_inline int charge_slab_page(struct page *page,
gfp_t gfp, int order,
struct kmem_cache *s)
{
+ int ret;
+
if (is_root_cache(s)) {
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
return 0;
}
+ ret = memcg_alloc_page_obj_cgroups(page, gfp, objs_per_slab(s));
+ if (ret)
+ return ret;
+
return memcg_charge_slab(page, gfp, order, s);
}
@@ -499,6 +546,7 @@ static __always_inline void uncharge_slab_page(struct page *page, int order,
return;
}
+ memcg_free_page_obj_cgroups(page);
memcg_uncharge_slab(page, order, s);
}
diff --git a/mm/slub.c b/mm/slub.c
index 8d16babe1829..a5fb0bb5c77a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -344,6 +344,11 @@ static inline unsigned int oo_objects(struct kmem_cache_order_objects x)
return x.x & OO_MASK;
}
+int objs_per_slab(struct kmem_cache *cache)
+{
+ return oo_objects(cache->oo);
+}
+
/*
* Per slab locking using the pagelock
*/
--
2.25.3
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