[PATCH v2 13/23] mm/slab: kmalloc: pass requests larger than order-1 page to page allocator
From: Hyeonggon Yoo
Date: Thu Apr 14 2022 - 05:02:14 EST
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@xxxxxxxxx>
---
Changes from previous series (Thanks to Vlastimil):
- Disable/Enable irqs around free_large_kmalloc()
- Do not lose NUMA locality in __do_kmalloc
- Some style fixes (use slab->slab_cache instead of virt_to_cache)
- Remove unsupported sizes in __kmalloc_index
Changes from v1:
- instead of defining varaible x, just casting to (void *) while calling free_large_kmalloc().
include/linux/slab.h | 23 +++++------------------
mm/slab.c | 44 ++++++++++++++++++++++++++++++--------------
mm/slab.h | 3 +++
mm/slab_common.c | 25 ++++++++++++++++++-------
mm/slub.c | 19 -------------------
5 files changed, 56 insertions(+), 58 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index ea168f8a248d..c8c82087c3f9 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -231,27 +231,17 @@ void kmem_dump_obj(void *object);
#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
@@ -403,10 +393,6 @@ 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()");
@@ -416,6 +402,7 @@ 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 b0aaca017f42..1dfe0f9d5882 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3533,7 +3533,7 @@ __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
void *ret;
if (unlikely(size > KMALLOC_MAX_CACHE_SIZE))
- return NULL;
+ return kmalloc_large_node(size, flags, node);
cachep = kmalloc_slab(size, flags);
if (unlikely(ZERO_OR_NULL_PTR(cachep)))
return cachep;
@@ -3607,15 +3607,25 @@ void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
{
struct kmem_cache *s;
size_t i;
+ struct folio *folio;
local_irq_disable();
for (i = 0; i < size; i++) {
void *objp = p[i];
- if (!orig_s) /* called via kfree_bulk */
- s = virt_to_cache(objp);
- else
+ if (!orig_s) {
+ 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;
@@ -3644,20 +3654,24 @@ 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);
@@ -4079,15 +4093,17 @@ 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 f7d018100994..b864c5bc4c25 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -681,6 +681,9 @@ 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 30684efc89d7..960cc07c3a91 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -764,8 +764,8 @@ 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),
@@ -789,11 +789,7 @@ 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)
};
/*
@@ -906,6 +902,21 @@ 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 892988990da7..1dc9e8eebb62 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1679,12 +1679,6 @@ 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)
{
@@ -3490,19 +3484,6 @@ 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