[PATCH v4 10/17] mm/slab: kmalloc: pass requests larger than order-1 page to page allocator

Hyeonggon Yoo
2022-08-17T10:19:55Z

There is not much benefit for serving large objects in kmalloc().
Let's pass large requests to page allocator like SLUB for better
maintenance of common code.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
---
include/linux/slab.h | 23 ++++-------------
mm/slab.c | 60 +++++++++++++++++++++++++++++++-------------
mm/slab.h | 3 +++
mm/slab_common.c | 25 ++++++++++++------
mm/slub.c | 19 --------------
5 files changed, 68 insertions(+), 62 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index fd2e129fc813..4ee5b2fed164 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -243,27 +243,17 @@ static inline unsigned int arch_slab_minalign(void)

#ifdef CONFIG_SLAB
/*
- * The largest kmalloc size supported by the SLAB allocators is
- * 32 megabyte (2^25) or the maximum allocatable page order if that is
- * less than 32 MB.
- *
- * WARNING: Its not easy to increase this value since the allocators have
- * to do various tricks to work around compiler limitations in order to
- * ensure proper constant folding.
+ * SLAB and SLUB directly allocates requests fitting in to an order-1 page
+ * (PAGE_SIZE*2). Larger requests are passed to the page allocator.
*/
-#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
- (MAX_ORDER + PAGE_SHIFT - 1) : 25)
-#define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH
+#define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
+#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 5
#endif
#endif

#ifdef CONFIG_SLUB
-/*
- * SLUB directly allocates requests fitting in to an order-1 page
- * (PAGE_SIZE*2). Larger requests are passed to the page allocator.
- */
#define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
#ifndef KMALLOC_SHIFT_LOW
@@ -415,10 +405,6 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
if (size <= 512 * 1024) return 19;
if (size <= 1024 * 1024) return 20;
if (size <= 2 * 1024 * 1024) return 21;
- if (size <= 4 * 1024 * 1024) return 22;
- if (size <= 8 * 1024 * 1024) return 23;
- if (size <= 16 * 1024 * 1024) return 24;
- if (size <= 32 * 1024 * 1024) return 25;

if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant)
BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
@@ -428,6 +414,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
/* Will never be reached. Needed because the compiler may complain */
return -1;
}
+static_assert(PAGE_SHIFT <= 20);
#define kmalloc_index(s) __kmalloc_index(s, true)
#endif /* !CONFIG_SLOB */

diff --git a/mm/slab.c b/mm/slab.c
index 8c08d7f3dead..10c9af904410 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3585,11 +3585,19 @@ __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
struct kmem_cache *cachep;
void *ret;

- if (unlikely(size > KMALLOC_MAX_CACHE_SIZE))
- return NULL;
+ if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) {
+ ret = kmalloc_large_node_notrace(size, flags, node);
+
+ trace_kmalloc_node(caller, ret, NULL, size,
+ PAGE_SIZE << get_order(size),
+ flags, node);
+ return ret;
+ }
+
cachep = kmalloc_slab(size, flags);
if (unlikely(ZERO_OR_NULL_PTR(cachep)))
return cachep;
+
ret = kmem_cache_alloc_node_trace(cachep, flags, node, size);
ret = kasan_kmalloc(cachep, ret, size, flags);

@@ -3664,17 +3672,27 @@ EXPORT_SYMBOL(kmem_cache_free);

void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
{
- struct kmem_cache *s;
- size_t i;

local_irq_disable();
- for (i = 0; i < size; i++) {
+ for (int i = 0; i < size; i++) {
void *objp = p[i];
+ struct kmem_cache *s;

- if (!orig_s) /* called via kfree_bulk */
- s = virt_to_cache(objp);
- else
+ if (!orig_s) {
+ struct folio *folio = virt_to_folio(objp);
+
+ /* called via kfree_bulk */
+ if (!folio_test_slab(folio)) {
+ local_irq_enable();
+ free_large_kmalloc(folio, objp);
+ local_irq_disable();
+ continue;
+ }
+ s = folio_slab(folio)->slab_cache;
+ } else {
s = cache_from_obj(orig_s, objp);
+ }
+
if (!s)
continue;

@@ -3703,20 +3721,24 @@ void kfree(const void *objp)
{
struct kmem_cache *c;
unsigned long flags;
+ struct folio *folio;

trace_kfree(_RET_IP_, objp);

if (unlikely(ZERO_OR_NULL_PTR(objp)))
return;
- local_irq_save(flags);
- kfree_debugcheck(objp);
- c = virt_to_cache(objp);
- if (!c) {
- local_irq_restore(flags);
+
+ folio = virt_to_folio(objp);
+ if (!folio_test_slab(folio)) {
+ free_large_kmalloc(folio, (void *)objp);
return;
}
- debug_check_no_locks_freed(objp, c->object_size);

+ c = folio_slab(folio)->slab_cache;
+
+ local_irq_save(flags);
+ kfree_debugcheck(objp);
+ debug_check_no_locks_freed(objp, c->object_size);
debug_check_no_obj_freed(objp, c->object_size);
__cache_free(c, (void *)objp, _RET_IP_);
local_irq_restore(flags);
@@ -4138,15 +4160,17 @@ void __check_heap_object(const void *ptr, unsigned long n,
size_t __ksize(const void *objp)
{
struct kmem_cache *c;
- size_t size;
+ struct folio *folio;

BUG_ON(!objp);
if (unlikely(objp == ZERO_SIZE_PTR))
return 0;

- c = virt_to_cache(objp);
- size = c ? c->object_size : 0;
+ folio = virt_to_folio(objp);
+ if (!folio_test_slab(folio))
+ return folio_size(folio);

- return size;
+ c = folio_slab(folio)->slab_cache;
+ return c->object_size;
}
EXPORT_SYMBOL(__ksize);
diff --git a/mm/slab.h b/mm/slab.h
index 40322bcf07be..381ba3e6b2a1 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -660,6 +660,9 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
print_tracking(cachep, x);
return cachep;
}
+
+void free_large_kmalloc(struct folio *folio, void *object);
+
#endif /* CONFIG_SLOB */

static inline size_t slab_ksize(const struct kmem_cache *s)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 51ccd0545816..5a2e81f42ee9 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -744,8 +744,8 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)

/*
* kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time.
- * kmalloc_index() supports up to 2^25=32MB, so the final entry of the table is
- * kmalloc-32M.
+ * kmalloc_index() supports up to 2^21=2MB, so the final entry of the table is
+ * kmalloc-2M.
*/
const struct kmalloc_info_struct kmalloc_info[] __initconst = {
INIT_KMALLOC_INFO(0, 0),
@@ -769,11 +769,7 @@ const struct kmalloc_info_struct kmalloc_info[] __initconst = {
INIT_KMALLOC_INFO(262144, 256k),
INIT_KMALLOC_INFO(524288, 512k),
INIT_KMALLOC_INFO(1048576, 1M),
- INIT_KMALLOC_INFO(2097152, 2M),
- INIT_KMALLOC_INFO(4194304, 4M),
- INIT_KMALLOC_INFO(8388608, 8M),
- INIT_KMALLOC_INFO(16777216, 16M),
- INIT_KMALLOC_INFO(33554432, 32M)
+ INIT_KMALLOC_INFO(2097152, 2M)
};

/*
@@ -886,6 +882,21 @@ void __init create_kmalloc_caches(slab_flags_t flags)
/* Kmalloc array is now usable */
slab_state = UP;
}
+
+void free_large_kmalloc(struct folio *folio, void *object)
+{
+ unsigned int order = folio_order(folio);
+
+ if (WARN_ON_ONCE(order == 0))
+ pr_warn_once("object pointer: 0x%p\n", object);
+
+ kmemleak_free(object);
+ kasan_kfree_large(object);
+
+ mod_lruvec_page_state(folio_page(folio, 0), NR_SLAB_UNRECLAIMABLE_B,
+ -(PAGE_SIZE << order));
+ __free_pages(folio_page(folio, 0), order);
+}
#endif /* !CONFIG_SLOB */

gfp_t kmalloc_fix_flags(gfp_t flags)
diff --git a/mm/slub.c b/mm/slub.c
index 165fe87af204..a659874c5d44 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1704,12 +1704,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct slab *slab,
* Hooks for other subsystems that check memory allocations. In a typical
* production configuration these hooks all should produce no code at all.
*/
-static __always_inline void kfree_hook(void *x)
-{
- kmemleak_free(x);
- kasan_kfree_large(x);
-}
-
static __always_inline bool slab_free_hook(struct kmem_cache *s,
void *x, bool init)
{
@@ -3550,19 +3544,6 @@ struct detached_freelist {
struct kmem_cache *s;
};

-static inline void free_large_kmalloc(struct folio *folio, void *object)
-{
- unsigned int order = folio_order(folio);
-
- if (WARN_ON_ONCE(order == 0))
- pr_warn_once("object pointer: 0x%p\n", object);
-
- kfree_hook(object);
- mod_lruvec_page_state(folio_page(folio, 0), NR_SLAB_UNRECLAIMABLE_B,
- -(PAGE_SIZE << order));
- __free_pages(folio_page(folio, 0), order);
-}
-
/*
* This function progressively scans the array with free objects (with
* a limited look ahead) and extract objects belonging to the same
--
2.32.0