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authorRoman Gushchin <guro@fb.com>2021-02-24 12:03:11 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-24 13:38:29 -0800
commit2e9bd483159939ed2c0704b914294653c8341d25 (patch)
tree878ce98090f4ad550e476a5e80c746f62c44fda8 /mm
parentcad8320b4b395702e49578580c70026c8271ea88 (diff)
mm: memcg/slab: pre-allocate obj_cgroups for slab caches with SLAB_ACCOUNT
In general it's unknown in advance if a slab page will contain accounted objects or not. In order to avoid memory waste, an obj_cgroup vector is allocated dynamically when a need to account of a new object arises. Such approach is memory efficient, but requires an expensive cmpxchg() to set up the memcg/objcgs pointer, because an allocation can race with a different allocation on another cpu. But in some common cases it's known for sure that a slab page will contain accounted objects: if the page belongs to a slab cache with a SLAB_ACCOUNT flag set. It includes such popular objects like vm_area_struct, anon_vma, task_struct, etc. In such cases we can pre-allocate the objcgs vector and simple assign it to the page without any atomic operations, because at this early stage the page is not visible to anyone else. A very simplistic benchmark (allocating 10000000 64-bytes objects in a row) shows ~15% win. In the real life it seems that most workloads are not very sensitive to the speed of (accounted) slab allocations. [guro@fb.com: open-code set_page_objcgs() and add some comments, by Johannes] Link: https://lkml.kernel.org/r/20201113001926.GA2934489@carbon.dhcp.thefacebook.com [akpm@linux-foundation.org: fix it for mm-slub-call-account_slab_page-after-slab-page-initialization-fix.patch] Link: https://lkml.kernel.org/r/20201110195753.530157-2-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c23
-rw-r--r--mm/slab.c2
-rw-r--r--mm/slab.h14
-rw-r--r--mm/slub.c2
4 files changed, 31 insertions, 10 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0b9bd354e97e..60ce452e42e6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2935,9 +2935,10 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg)
#ifdef CONFIG_MEMCG_KMEM
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
- gfp_t gfp)
+ gfp_t gfp, bool new_page)
{
unsigned int objects = objs_per_slab_page(s, page);
+ unsigned long memcg_data;
void *vec;
vec = kcalloc_node(objects, sizeof(struct obj_cgroup *), gfp,
@@ -2945,11 +2946,25 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
if (!vec)
return -ENOMEM;
- if (!set_page_objcgs(page, vec))
+ memcg_data = (unsigned long) vec | MEMCG_DATA_OBJCGS;
+ if (new_page) {
+ /*
+ * If the slab page is brand new and nobody can yet access
+ * it's memcg_data, no synchronization is required and
+ * memcg_data can be simply assigned.
+ */
+ page->memcg_data = memcg_data;
+ } else if (cmpxchg(&page->memcg_data, 0, memcg_data)) {
+ /*
+ * If the slab page is already in use, somebody can allocate
+ * and assign obj_cgroups in parallel. In this case the existing
+ * objcg vector should be reused.
+ */
kfree(vec);
- else
- kmemleak_not_leak(vec);
+ return 0;
+ }
+ kmemleak_not_leak(vec);
return 0;
}
diff --git a/mm/slab.c b/mm/slab.c
index cdad64b2836d..9c9e0c255c4b 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1379,7 +1379,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
return NULL;
}
- account_slab_page(page, cachep->gfporder, cachep);
+ account_slab_page(page, cachep->gfporder, cachep, flags);
__SetPageSlab(page);
/* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
if (sk_memalloc_socks() && page_is_pfmemalloc(page))
diff --git a/mm/slab.h b/mm/slab.h
index 48dc466a3791..076582f58f68 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -238,7 +238,7 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
#ifdef CONFIG_MEMCG_KMEM
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
- gfp_t gfp);
+ gfp_t gfp, bool new_page);
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
@@ -315,7 +315,8 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
page = virt_to_head_page(p[i]);
if (!page_objcgs(page) &&
- memcg_alloc_page_obj_cgroups(page, s, flags)) {
+ memcg_alloc_page_obj_cgroups(page, s, flags,
+ false)) {
obj_cgroup_uncharge(objcg, obj_full_size(s));
continue;
}
@@ -379,7 +380,8 @@ static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
}
static inline int memcg_alloc_page_obj_cgroups(struct page *page,
- struct kmem_cache *s, gfp_t gfp)
+ struct kmem_cache *s, gfp_t gfp,
+ bool new_page)
{
return 0;
}
@@ -420,8 +422,12 @@ static inline struct kmem_cache *virt_to_cache(const void *obj)
}
static __always_inline void account_slab_page(struct page *page, int order,
- struct kmem_cache *s)
+ struct kmem_cache *s,
+ gfp_t gfp)
{
+ if (memcg_kmem_enabled() && (s->flags & SLAB_ACCOUNT))
+ memcg_alloc_page_obj_cgroups(page, s, gfp, true);
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
}
diff --git a/mm/slub.c b/mm/slub.c
index e0fef8f8d4bf..ca566361561e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1785,7 +1785,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
page->objects = oo_objects(oo);
- account_slab_page(page, oo_order(oo), s);
+ account_slab_page(page, oo_order(oo), s, flags);
page->slab_cache = s;
__SetPageSlab(page);