From: Johannes Berg <johannes.berg@xxxxxxxxx> 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. Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> --- Perhaps instead it should go the other way around, and kmemleak could even use/access the stack trace that's already in there ... But I don't really care too much, I can just turn off slub debug for the kmemleak caches via the command line anyway :-) --- mm/slub.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 34dcc09e2ec9..625a32a6645b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1446,7 +1446,16 @@ slab_flags_t kmem_cache_flags(unsigned int object_size, } } - return flags | slub_debug; + flags |= slub_debug; + + /* + * If the slab cache is for debugging (e.g. kmemleak) then + * don't store user (stack trace) information. + */ + if (flags & SLAB_NOLEAKTRACE) + flags &= ~SLAB_STORE_USER; + + return flags; } #else /* !CONFIG_SLUB_DEBUG */ static inline void setup_object_debug(struct kmem_cache *s, -- 2.26.2
