Commit ca220593 authored by Johannes Berg's avatar Johannes Berg Committed by Linus Torvalds
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mm/slub: disable user tracing for kmemleak caches by default 

If kmemleak is enabled, it uses a kmem cache for its own objects.  These
objects are used to hold information kmemleak uses, including a stack
trace.  If slub_debug is also turned on, each of them has *another* stack
trace, so the overhead adds up, and on my tests (on ARCH=um, admittedly)
2/3rds of the allocations end up being doing the stack tracing.

Turn off SLAB_STORE_USER if SLAB_NOLEAKTRACE was given, to avoid storing
the essentially same data twice.

Link: https://lkml.kernel.org/r/20210113215114.d94efa13ba30.I117b6764e725b3192318bbcf4269b13b709539ae@changeid


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0b411634

mm/slub.c

+10 −1
Original line number Diff line number Diff line
@@ -1413,6 +1413,15 @@ slab_flags_t kmem_cache_flags(unsigned int object_size, 
	size_t len;

	char *next_block;

	slab_flags_t block_flags;

	slab_flags_t slub_debug_local = slub_debug;



	/*

	 * If the slab cache is for debugging (e.g. kmemleak) then

	 * don't store user (stack trace) information by default,

	 * but let the user enable it via the command line below.

	 */

	if (flags & SLAB_NOLEAKTRACE)

		slub_debug_local &= ~SLAB_STORE_USER;



	len = strlen(name);

	next_block = slub_debug_string;
@@ -1447,7 +1456,7 @@ slab_flags_t kmem_cache_flags(unsigned int object_size, 
		}

	}



	return flags | slub_debug;

	return flags | slub_debug_local;

}

#else /* !CONFIG_SLUB_DEBUG */

static inline void setup_object_debug(struct kmem_cache *s,