linux-kernel - [PATCH 11/12] mm, slub: don't aggressively inline with CONFIG_SLUB

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Date:   Mon, 21 Nov 2022 18:12:01 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, patches@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 11/12] mm, slub: don't aggressively inline with CONFIG_SLUB_TINY

SLUB fastpaths use __always_inline to avoid function calls. With
CONFIG_SLUB_TINY we would rather save the memory. Add a
__fastpath_inline macro that's __always_inline normally but empty with
CONFIG_SLUB_TINY.

bloat-o-meter results on x86_64 mm/slub.o:

add/remove: 3/1 grow/shrink: 1/8 up/down: 865/-1784 (-919)
Function                                     old     new   delta
kmem_cache_free                               20     281    +261
slab_alloc_node.isra                           -     245    +245
slab_free.constprop.isra                       -     231    +231
__kmem_cache_alloc_lru.isra                    -     128    +128
__kmem_cache_release                          88      83      -5
__kmem_cache_create                         1446    1436     -10
__kmem_cache_free                            271     142    -129
kmem_cache_alloc_node                        330     127    -203
kmem_cache_free_bulk.part                    826     613    -213
__kmem_cache_alloc_node                      230      10    -220
kmem_cache_alloc_lru                         325      12    -313
kmem_cache_alloc                             325      10    -315
kmem_cache_free.part                         376       -    -376
Total: Before=26103, After=25184, chg -3.52%

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 7f1cd702c3b4..d54466e76503 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -187,6 +187,12 @@ do {					\
 #define USE_LOCKLESS_FAST_PATH()	(false)
 #endif
 
+#ifndef CONFIG_SLUB_TINY
+#define __fastpath_inline __always_inline
+#else
+#define __fastpath_inline
+#endif
+
 #ifdef CONFIG_SLUB_DEBUG
 #ifdef CONFIG_SLUB_DEBUG_ON
 DEFINE_STATIC_KEY_TRUE(slub_debug_enabled);
@@ -3386,7 +3392,7 @@ static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s,
  *
  * Otherwise we can simply pick the next object from the lockless free list.
  */
-static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_lru *lru,
+static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list_lru *lru,
 		gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
 {
 	void *object;
@@ -3412,13 +3418,13 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_l
 	return object;
 }
 
-static __always_inline void *slab_alloc(struct kmem_cache *s, struct list_lru *lru,
+static __fastpath_inline void *slab_alloc(struct kmem_cache *s, struct list_lru *lru,
 		gfp_t gfpflags, unsigned long addr, size_t orig_size)
 {
 	return slab_alloc_node(s, lru, gfpflags, NUMA_NO_NODE, addr, orig_size);
 }
 
-static __always_inline
+static __fastpath_inline
 void *__kmem_cache_alloc_lru(struct kmem_cache *s, struct list_lru *lru,
 			     gfp_t gfpflags)
 {
@@ -3733,7 +3739,7 @@ static void do_slab_free(struct kmem_cache *s,
 }
 #endif /* CONFIG_SLUB_TINY */
 
-static __always_inline void slab_free(struct kmem_cache *s, struct slab *slab,
+static __fastpath_inline void slab_free(struct kmem_cache *s, struct slab *slab,
 				      void *head, void *tail, void **p, int cnt,
 				      unsigned long addr)
 {
-- 
2.38.1