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mm/slub: disable user tracing for kmemleak caches by default

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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: Johannes Berg <johannes.berg@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Vlastimil 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Berg 2021-02-24 12:01:04 -08:00 committed by Linus Torvalds
parent 0b41163407
commit ca22059320
1 changed files with 10 additions and 1 deletions
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11
mm/slub.c
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@ -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,