From: Johannes Berg <johannes.berg@xxxxxxxxx> Subject: 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: Johannes Berg <johannes.berg@xxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/mm/slub.c~mm-slub-disable-user-tracing-for-kmemleak-caches-by-default +++ a/mm/slub.c @@ -1413,6 +1413,15 @@ slab_flags_t kmem_cache_flags(unsigned i 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 i } } - return flags | slub_debug; + return flags | slub_debug_local; } #else /* !CONFIG_SLUB_DEBUG */ static inline void setup_object_debug(struct kmem_cache *s, _
