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mm/slab_common: commonize slab merge logic
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Slab merge is good feature to reduce fragmentation.  Now, it is only
applied to SLUB, but, it would be good to apply it to SLAB.  This patch is
preparation step to apply slab merge to SLAB by commonizing slab merge
logic.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Joonsoo Kim authored and Linus Torvalds committed Oct 10, 2014
1 parent 9163582 commit 423c929
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Showing 4 changed files with 117 additions and 94 deletions.
14 changes: 9 additions & 5 deletions Documentation/kernel-parameters.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -3158,6 +3158,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.

slram= [HW,MTD]

slab_nomerge [MM]
Disable merging of slabs with similar size. May be
necessary if there is some reason to distinguish
allocs to different slabs. Debug options disable
merging on their own.
For more information see Documentation/vm/slub.txt.

slab_max_order= [MM, SLAB]
Determines the maximum allowed order for slabs.
A high setting may cause OOMs due to memory
Expand Down Expand Up @@ -3193,11 +3200,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
For more information see Documentation/vm/slub.txt.

slub_nomerge [MM, SLUB]
Disable merging of slabs with similar size. May be
necessary if there is some reason to distinguish
allocs to different slabs. Debug options disable
merging on their own.
For more information see Documentation/vm/slub.txt.
Same with slab_nomerge. This is supported for legacy.
See slab_nomerge for more information.

smart2= [HW]
Format: <io1>[,<io2>[,...,<io8>]]
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15 changes: 15 additions & 0 deletions mm/slab.h
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Original file line number Diff line number Diff line change
Expand Up @@ -88,15 +88,30 @@ extern void create_boot_cache(struct kmem_cache *, const char *name,
size_t size, unsigned long flags);

struct mem_cgroup;

int slab_unmergeable(struct kmem_cache *s);
struct kmem_cache *find_mergeable(size_t size, size_t align,
unsigned long flags, const char *name, void (*ctor)(void *));
#ifdef CONFIG_SLUB
struct kmem_cache *
__kmem_cache_alias(const char *name, size_t size, size_t align,
unsigned long flags, void (*ctor)(void *));

unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long flags, const char *name,
void (*ctor)(void *));
#else
static inline struct kmem_cache *
__kmem_cache_alias(const char *name, size_t size, size_t align,
unsigned long flags, void (*ctor)(void *))
{ return NULL; }

static inline unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long flags, const char *name,
void (*ctor)(void *))
{
return flags;
}
#endif


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91 changes: 91 additions & 0 deletions mm/slab_common.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,34 @@ LIST_HEAD(slab_caches);
DEFINE_MUTEX(slab_mutex);
struct kmem_cache *kmem_cache;

/*
* Set of flags that will prevent slab merging
*/
#define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
SLAB_FAILSLAB)

#define SLAB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
SLAB_CACHE_DMA | SLAB_NOTRACK)

/*
* Merge control. If this is set then no merging of slab caches will occur.
* (Could be removed. This was introduced to pacify the merge skeptics.)
*/
static int slab_nomerge;

static int __init setup_slab_nomerge(char *str)
{
slab_nomerge = 1;
return 1;
}

#ifdef CONFIG_SLUB
__setup_param("slub_nomerge", slub_nomerge, setup_slab_nomerge, 0);
#endif

__setup("slab_nomerge", setup_slab_nomerge);

/*
* Determine the size of a slab object
*/
Expand Down Expand Up @@ -115,6 +143,69 @@ int memcg_update_all_caches(int num_memcgs)
}
#endif

/*
* Find a mergeable slab cache
*/
int slab_unmergeable(struct kmem_cache *s)
{
if (slab_nomerge || (s->flags & SLAB_NEVER_MERGE))
return 1;

if (!is_root_cache(s))
return 1;

if (s->ctor)
return 1;

/*
* We may have set a slab to be unmergeable during bootstrap.
*/
if (s->refcount < 0)
return 1;

return 0;
}

struct kmem_cache *find_mergeable(size_t size, size_t align,
unsigned long flags, const char *name, void (*ctor)(void *))
{
struct kmem_cache *s;

if (slab_nomerge || (flags & SLAB_NEVER_MERGE))
return NULL;

if (ctor)
return NULL;

size = ALIGN(size, sizeof(void *));
align = calculate_alignment(flags, align, size);
size = ALIGN(size, align);
flags = kmem_cache_flags(size, flags, name, NULL);

list_for_each_entry(s, &slab_caches, list) {
if (slab_unmergeable(s))
continue;

if (size > s->size)
continue;

if ((flags & SLAB_MERGE_SAME) != (s->flags & SLAB_MERGE_SAME))
continue;
/*
* Check if alignment is compatible.
* Courtesy of Adrian Drzewiecki
*/
if ((s->size & ~(align - 1)) != s->size)
continue;

if (s->size - size >= sizeof(void *))
continue;

return s;
}
return NULL;
}

/*
* Figure out what the alignment of the objects will be given a set of
* flags, a user specified alignment and the size of the objects.
Expand Down
91 changes: 2 additions & 89 deletions mm/slub.c
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Original file line number Diff line number Diff line change
Expand Up @@ -169,16 +169,6 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
*/
#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)

/*
* Set of flags that will prevent slab merging
*/
#define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
SLAB_FAILSLAB)

#define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
SLAB_CACHE_DMA | SLAB_NOTRACK)

#define OO_SHIFT 16
#define OO_MASK ((1 << OO_SHIFT) - 1)
#define MAX_OBJS_PER_PAGE 32767 /* since page.objects is u15 */
Expand Down Expand Up @@ -1176,7 +1166,7 @@ static int __init setup_slub_debug(char *str)

__setup("slub_debug", setup_slub_debug);

static unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long flags, const char *name,
void (*ctor)(void *))
{
Expand Down Expand Up @@ -1208,7 +1198,7 @@ static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n,
struct page *page) {}
static inline void remove_full(struct kmem_cache *s, struct kmem_cache_node *n,
struct page *page) {}
static inline unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long kmem_cache_flags(unsigned long object_size,
unsigned long flags, const char *name,
void (*ctor)(void *))
{
Expand Down Expand Up @@ -2718,12 +2708,6 @@ static int slub_min_order;
static int slub_max_order = PAGE_ALLOC_COSTLY_ORDER;
static int slub_min_objects;

/*
* Merge control. If this is set then no merging of slab caches will occur.
* (Could be removed. This was introduced to pacify the merge skeptics.)
*/
static int slub_nomerge;

/*
* Calculate the order of allocation given an slab object size.
*
Expand Down Expand Up @@ -3252,14 +3236,6 @@ static int __init setup_slub_min_objects(char *str)

__setup("slub_min_objects=", setup_slub_min_objects);

static int __init setup_slub_nomerge(char *str)
{
slub_nomerge = 1;
return 1;
}

__setup("slub_nomerge", setup_slub_nomerge);

void *__kmalloc(size_t size, gfp_t flags)
{
struct kmem_cache *s;
Expand Down Expand Up @@ -3637,69 +3613,6 @@ void __init kmem_cache_init_late(void)
{
}

/*
* Find a mergeable slab cache
*/
static int slab_unmergeable(struct kmem_cache *s)
{
if (slub_nomerge || (s->flags & SLUB_NEVER_MERGE))
return 1;

if (!is_root_cache(s))
return 1;

if (s->ctor)
return 1;

/*
* We may have set a slab to be unmergeable during bootstrap.
*/
if (s->refcount < 0)
return 1;

return 0;
}

static struct kmem_cache *find_mergeable(size_t size, size_t align,
unsigned long flags, const char *name, void (*ctor)(void *))
{
struct kmem_cache *s;

if (slub_nomerge || (flags & SLUB_NEVER_MERGE))
return NULL;

if (ctor)
return NULL;

size = ALIGN(size, sizeof(void *));
align = calculate_alignment(flags, align, size);
size = ALIGN(size, align);
flags = kmem_cache_flags(size, flags, name, NULL);

list_for_each_entry(s, &slab_caches, list) {
if (slab_unmergeable(s))
continue;

if (size > s->size)
continue;

if ((flags & SLUB_MERGE_SAME) != (s->flags & SLUB_MERGE_SAME))
continue;
/*
* Check if alignment is compatible.
* Courtesy of Adrian Drzewiecki
*/
if ((s->size & ~(align - 1)) != s->size)
continue;

if (s->size - size >= sizeof(void *))
continue;

return s;
}
return NULL;
}

struct kmem_cache *
__kmem_cache_alias(const char *name, size_t size, size_t align,
unsigned long flags, void (*ctor)(void *))
Expand Down

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