The patch titled
Subject: mm, slub: introduce static key for slub_debug()
has been added to the -mm tree. Its filename is
mm-slub-introduce-static-key-for-slub_debug.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-slub-introduce-static-key-for-slub_debug.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-introduce-static-key-for-slub_debug.patch
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, slub: introduce static key for slub_debug()
One advantage of CONFIG_SLUB_DEBUG is that a generic distro kernel can be
built with the option enabled, but it's inactive until simply enabled on
boot, without rebuilding the kernel. With a static key, we can further
eliminate the overhead of checking whether a cache has a particular debug
flag enabled if we know that there are no such caches (slub_debug was not
enabled during boot). We use the same mechanism also for e.g.
page_owner, debug_pagealloc or kmemcg functionality.
This patch introduces the static key and makes the general check for
per-cache debug flags kmem_cache_debug() use it. This benefits several
call sites, including (slow path but still rather frequent) __slab_free().
The next patches will add more uses.
Link: http://lkml.kernel.org/r/20200610163135.17364-7-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
--- a/mm/slub.c~mm-slub-introduce-static-key-for-slub_debug
+++ a/mm/slub.c
@@ -114,13 +114,21 @@
* the fast path and disables lockless freelists.
*/
+#ifdef CONFIG_SLUB_DEBUG
+#ifdef CONFIG_SLUB_DEBUG_ON
+DEFINE_STATIC_KEY_TRUE(slub_debug_enabled);
+#else
+DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
+#endif
+#endif
+
static inline int kmem_cache_debug(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_DEBUG
- return unlikely(s->flags & SLAB_DEBUG_FLAGS);
-#else
- return 0;
+ if (static_branch_unlikely(&slub_debug_enabled))
+ return s->flags & SLAB_DEBUG_FLAGS;
#endif
+ return 0;
}
void *fixup_red_left(struct kmem_cache *s, void *p)
@@ -1389,6 +1397,8 @@ static int __init setup_slub_debug(char
slub_debug_string = saved_str;
}
out:
+ if (slub_debug != 0 || slub_debug_string)
+ static_branch_enable(&slub_debug_enabled);
if ((static_branch_unlikely(&init_on_alloc) ||
static_branch_unlikely(&init_on_free)) &&
(slub_debug & SLAB_POISON))
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-slub-extend-slub_debug-syntax-for-multiple-blocks.patch
mm-slub-make-some-slub_debug-related-attributes-read-only.patch
mm-slub-remove-runtime-allocation-order-changes.patch
mm-slub-make-remaining-slub_debug-related-attributes-read-only.patch
mm-slub-make-reclaim_account-attribute-read-only.patch
mm-slub-introduce-static-key-for-slub_debug.patch
mm-slub-introduce-kmem_cache_debug_flags.patch
mm-slub-extend-checks-guarded-by-slub_debug-static-key.patch
mm-slab-slub-move-and-improve-cache_from_obj.patch
