The patch titled
Subject: mm: memcg/slab: pre-allocate obj_cgroups for slab caches with SLAB_ACCOUNT
has been added to the -mm tree. Its filename is
mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account.patch
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------------------------------------------------------
From: Roman Gushchin <guro@xxxxxx>
Subject: 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.
Link: https://lkml.kernel.org/r/20201110195753.530157-2-guro@xxxxxx
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 14 ++++++++++----
mm/memcontrol.c | 4 ++--
mm/slab.c | 2 +-
mm/slab.h | 14 ++++++++++----
4 files changed, 23 insertions(+), 11 deletions(-)
--- a/include/linux/memcontrol.h~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/include/linux/memcontrol.h
@@ -484,14 +484,20 @@ static inline struct obj_cgroup **page_o
* set_page_objcgs - associate a page with a object cgroups vector
* @page: a pointer to the page struct
* @objcgs: a pointer to the object cgroups vector
+ * @atomic: save the value atomically
*
* Atomically associates a page with a vector of object cgroups.
*/
static inline bool set_page_objcgs(struct page *page,
- struct obj_cgroup **objcgs)
+ struct obj_cgroup **objcgs, bool atomic)
{
- return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs |
- MEMCG_DATA_OBJCGS);
+ unsigned long memcg_data = (unsigned long) objcgs | MEMCG_DATA_OBJCGS;
+
+ if (atomic)
+ return !cmpxchg(&page->memcg_data, 0, memcg_data);
+
+ page->memcg_data = memcg_data;
+ return true;
}
#else
static inline struct obj_cgroup **page_objcgs(struct page *page)
@@ -505,7 +511,7 @@ static inline struct obj_cgroup **page_o
}
static inline bool set_page_objcgs(struct page *page,
- struct obj_cgroup **objcgs)
+ struct obj_cgroup **objcgs, bool atomic)
{
return true;
}
--- a/mm/memcontrol.c~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/mm/memcontrol.c
@@ -2879,7 +2879,7 @@ static void commit_charge(struct page *p
#ifdef CONFIG_MEMCG_KMEM
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
- gfp_t gfp)
+ gfp_t gfp, bool atomic)
{
unsigned int objects = objs_per_slab_page(s, page);
void *vec;
@@ -2889,7 +2889,7 @@ int memcg_alloc_page_obj_cgroups(struct
if (!vec)
return -ENOMEM;
- if (!set_page_objcgs(page, vec))
+ if (!set_page_objcgs(page, vec, atomic))
kfree(vec);
else
kmemleak_not_leak(vec);
--- a/mm/slab.c~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/mm/slab.c
@@ -1379,7 +1379,7 @@ static struct page *kmem_getpages(struct
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))
--- a/mm/slab.h~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/mm/slab.h
@@ -240,7 +240,7 @@ static inline bool kmem_cache_debug_flag
#ifdef CONFIG_MEMCG_KMEM
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
- gfp_t gfp);
+ gfp_t gfp, bool atomic);
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
@@ -307,7 +307,8 @@ static inline void memcg_slab_post_alloc
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,
+ true)) {
obj_cgroup_uncharge(objcg, obj_full_size(s));
continue;
}
@@ -371,7 +372,8 @@ static inline struct mem_cgroup *memcg_f
}
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 atomic)
{
return 0;
}
@@ -412,8 +414,12 @@ static inline struct kmem_cache *virt_to
}
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, false);
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
}
_
Patches currently in -mm which might be from guro@xxxxxx are
mm-memcontrol-use-helpers-to-read-pages-memcg-data.patch
mm-memcontrol-slab-use-helpers-to-access-slab-pages-memcg_data.patch
mm-introduce-page-memcg-flags.patch
mm-convert-page-kmemcg-type-to-a-page-memcg-flag.patch
mm-memcg-fix-obsolete-code-comments.patch
mm-slub-call-account_slab_page-after-slab-page-initialization.patch
mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account.patch
mm-vmstat-fix-proc-sys-vm-stat_refresh-generating-false-warnings.patch
mm-vmstat-fix-proc-sys-vm-stat_refresh-generating-false-warnings-fix.patch
