From: Johannes Berg <johannes@sipsolutions.net>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Johannes Berg <johannes.berg@intel.com>
Subject: [PATCH] mm/slub: disable user tracing for kmemleak caches
Date: Wed, 13 Jan 2021 17:09:31 +0100 [thread overview]
Message-ID: <20210113170931.929f808099d2.I117b6764e725b3192318bbcf4269b13b709539ae@changeid> (raw)
From: Johannes Berg <johannes.berg@intel.com>
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@intel.com>
---
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
next reply other threads:[~2021-01-13 16:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 16:09 Johannes Berg [this message]
2021-01-13 16:59 ` [PATCH] mm/slub: disable user tracing for kmemleak caches Vlastimil Babka
2021-01-13 18:11 ` Johannes Berg
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