The patch titled
Subject: mm: memcg/slab: pre-allocate obj_cgroups for slab caches with SLAB_ACCOUNT
has been removed from the -mm tree. Its filename was
mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
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.
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@xxxxxx: open-code set_page_objcgs() and add some comments, by Johannes]
Link: https://lkml.kernel.org/r/20201113001926.GA2934489@xxxxxxxxxxxxxxxxxxxxxxxxxxx
[akpm@xxxxxxxxxxxxxxxxxxxx: 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@xxxxxx
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 19 -------------------
mm/memcontrol.c | 23 +++++++++++++++++++----
mm/slab.c | 2 +-
mm/slab.h | 14 ++++++++++----
mm/slub.c | 2 +-
5 files changed, 31 insertions(+), 29 deletions(-)
--- a/include/linux/memcontrol.h~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/include/linux/memcontrol.h
@@ -475,19 +475,6 @@ static inline struct obj_cgroup **page_o
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
-/*
- * 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
- *
- * Atomically associates a page with a vector of object cgroups.
- */
-static inline bool set_page_objcgs(struct page *page,
- struct obj_cgroup **objcgs)
-{
- return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs |
- MEMCG_DATA_OBJCGS);
-}
#else
static inline struct obj_cgroup **page_objcgs(struct page *page)
{
@@ -498,12 +485,6 @@ static inline struct obj_cgroup **page_o
{
return NULL;
}
-
-static inline bool set_page_objcgs(struct page *page,
- struct obj_cgroup **objcgs)
-{
- return true;
-}
#endif
static __always_inline bool memcg_stat_item_in_bytes(int idx)
--- a/mm/memcontrol.c~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/mm/memcontrol.c
@@ -2935,9 +2935,10 @@ 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 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
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;
}
--- 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
@@ -238,7 +238,7 @@ 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 new_page);
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
@@ -315,7 +315,8 @@ 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,
+ false)) {
obj_cgroup_uncharge(objcg, obj_full_size(s));
continue;
}
@@ -379,7 +380,8 @@ 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 new_page)
{
return 0;
}
@@ -420,8 +422,12 @@ 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, true);
+
mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
PAGE_SIZE << order);
}
--- a/mm/slub.c~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account
+++ a/mm/slub.c
@@ -1785,7 +1785,7 @@ static struct page *allocate_slab(struct
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);
_
Patches currently in -mm which might be from guro@xxxxxx are
mm-cma-allocate-cma-areas-bottom-up.patch
mm-cma-allocate-cma-areas-bottom-up-fix.patch
mm-cma-allocate-cma-areas-bottom-up-fix-2.patch
mm-cma-allocate-cma-areas-bottom-up-fix-3.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
