[PATCH v2 4/6] slab: add SLAB_ACCOUNT flag

Vladimir Davydov
2015-11-10T18:34:46Z

Currently, if we want to account all objects of a particular kmem cache,
we have to pass __GFP_ACCOUNT to each kmem_cache_alloc call, which is
inconvenient. This patch introduces SLAB_ACCOUNT flag which if passed to
kmem_cache_create will force accounting for every allocation from this
cache even if __GFP_ACCOUNT is not passed.

This patch does not make any of the existing caches use this flag - it
will be done later in the series.

Note, a cache with SLAB_ACCOUNT cannot be merged with a cache w/o
SLAB_ACCOUNT, i.e. using this flag will probably reduce the number of
merged slabs even if kmem accounting is not used (only compiled in).

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
---
include/linux/memcontrol.h | 15 +++++++--------
include/linux/slab.h | 5 +++++
mm/memcontrol.c | 8 +++++++-
mm/slab.h | 5 +++--
mm/slab_common.c | 3 ++-
mm/slub.c | 2 ++
6 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c9d9a8e7b45f..5c97265c1c6e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -766,15 +766,13 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
return memcg ? memcg->kmemcg_id : -1;
}

-struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep);
+struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp);
void __memcg_kmem_put_cache(struct kmem_cache *cachep);

-static inline bool __memcg_kmem_bypass(gfp_t gfp)
+static inline bool __memcg_kmem_bypass(void)
{
if (!memcg_kmem_enabled())
return true;
- if (!(gfp & __GFP_ACCOUNT))
- return true;
if (in_interrupt() || (!current->mm) || (current->flags & PF_KTHREAD))
return true;
return false;
@@ -791,7 +789,9 @@ static inline bool __memcg_kmem_bypass(gfp_t gfp)
static __always_inline int memcg_kmem_charge(struct page *page,
gfp_t gfp, int order)
{
- if (__memcg_kmem_bypass(gfp))
+ if (__memcg_kmem_bypass())
+ return 0;
+ if (!(gfp & __GFP_ACCOUNT))
return 0;
return __memcg_kmem_charge(page, gfp, order);
}
@@ -810,16 +810,15 @@ static __always_inline void memcg_kmem_uncharge(struct page *page, int order)
/**
* memcg_kmem_get_cache: selects the correct per-memcg cache for allocation
* @cachep: the original global kmem cache
- * @gfp: allocation flags.
*
* All memory allocated from a per-memcg cache is charged to the owner memcg.
*/
static __always_inline struct kmem_cache *
memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
{
- if (__memcg_kmem_bypass(gfp))
+ if (__memcg_kmem_bypass())
return cachep;
- return __memcg_kmem_get_cache(cachep);
+ return __memcg_kmem_get_cache(cachep, gfp);
}

static __always_inline void memcg_kmem_put_cache(struct kmem_cache *cachep)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 7c82e3b307a3..20168c6ffe89 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -86,6 +86,11 @@
#else
# define SLAB_FAILSLAB 0x00000000UL
#endif
+#ifdef CONFIG_MEMCG_KMEM
+# define SLAB_ACCOUNT 0x04000000UL /* Account to memcg */
+#else
+# define SLAB_ACCOUNT 0x00000000UL
+#endif

/* The following flags affect the page allocator grouping pages by mobility */
#define SLAB_RECLAIM_ACCOUNT 0x00020000UL /* Objects are reclaimable */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bc502e590366..06e4f538e38e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2332,7 +2332,7 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
* Can't be called in interrupt context or from kernel threads.
* This function needs to be called with rcu_read_lock() held.
*/
-struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep)
+struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
{
struct mem_cgroup *memcg;
struct kmem_cache *memcg_cachep;
@@ -2340,6 +2340,12 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep)

VM_BUG_ON(!is_root_cache(cachep));

+ if (cachep->flags & SLAB_ACCOUNT)
+ gfp |= __GFP_ACCOUNT;
+
+ if (!(gfp & __GFP_ACCOUNT))
+ return cachep;
+
if (current->memcg_kmem_skip_account)
return cachep;

diff --git a/mm/slab.h b/mm/slab.h
index 27492eb678f7..2778de8673bd 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -128,10 +128,11 @@ static inline unsigned long kmem_cache_flags(unsigned long object_size,

#if defined(CONFIG_SLAB)
#define SLAB_CACHE_FLAGS (SLAB_MEM_SPREAD | SLAB_NOLEAKTRACE | \
- SLAB_RECLAIM_ACCOUNT | SLAB_TEMPORARY | SLAB_NOTRACK)
+ SLAB_RECLAIM_ACCOUNT | SLAB_TEMPORARY | \
+ SLAB_NOTRACK | SLAB_ACCOUNT)
#elif defined(CONFIG_SLUB)
#define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \
- SLAB_TEMPORARY | SLAB_NOTRACK)
+ SLAB_TEMPORARY | SLAB_NOTRACK | SLAB_ACCOUNT)
#else
#define SLAB_CACHE_FLAGS (0)
#endif
diff --git a/mm/slab_common.c b/mm/slab_common.c
index d88e97c10a2e..698b2c97b22b 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -37,7 +37,8 @@ struct kmem_cache *kmem_cache;
SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
SLAB_FAILSLAB)

-#define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | SLAB_NOTRACK)
+#define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
+ SLAB_NOTRACK | SLAB_ACCOUNT)

/*
* Merge control. If this is set then no merging of slab caches will occur.
diff --git a/mm/slub.c b/mm/slub.c
index 75a5fa92ac2a..b037cea9cfeb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5247,6 +5247,8 @@ static char *create_unique_id(struct kmem_cache *s)
*p++ = 'F';
if (!(s->flags & SLAB_NOTRACK))
*p++ = 't';
+ if (s->flags & SLAB_ACCOUNT)
+ *p++ = 'A';
if (p != name + 1)
*p++ = '-';
p += sprintf(p, "%07d", s->size);
--
2.1.4