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>,
Vlastimil Babka <vbabka@suse.cz>,
Johannes Berg <johannes.berg@intel.com>
Subject: [PATCH v2] mm/slub: disable user tracing for kmemleak caches by default
Date: Wed, 13 Jan 2021 21:51:14 +0100 [thread overview]
Message-ID: <20210113215114.d94efa13ba30.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 :-)
v2:
- strip SLAB_STORE_USER only coming from slub_debug so that the
command line args always take effect
---
mm/slub.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/mm/slub.c b/mm/slub.c
index 34dcc09e2ec9..a66c9948c529 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1412,6 +1412,15 @@ 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;
@@ -1446,7 +1455,7 @@ 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,
--
2.26.2
next reply other threads:[~2021-01-13 20:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 20:51 Johannes Berg [this message]
2021-01-14 11:07 ` [PATCH v2] mm/slub: disable user tracing for kmemleak caches by default Vlastimil Babka
2021-01-14 11:13 ` Catalin Marinas
2021-01-15 19:41 ` David Rientjes
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