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authorVlastimil Babka <vbabka@suse.cz>2020-08-07 09:18:51 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 21:33:22 +0300
commitca0cab65ea2b8c1527dc48c8dfd38ae055f5f241 (patch)
tree83b70975ae67204d8c10617eb80790e5aa2cd600 /mm/slub.c
parent8f58119ac49c03c5a0879353661c586b0436c250 (diff)
downloadlinux-ca0cab65ea2b8c1527dc48c8dfd38ae055f5f241.tar.xz
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. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Jann Horn <jannh@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Link: http://lkml.kernel.org/r/20200610163135.17364-7-vbabka@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 617cf1fff128..8adab4c5296d 100644
--- a/mm/slub.c
+++ b/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 *str)
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))