The patch titled
Subject: mm/slub: disable user tracing for kmemleak caches by default
has been added to the -mm tree. Its filename is
mm-slub-disable-user-tracing-for-kmemleak-caches-by-default.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-slub-disable-user-tracing-for-kmemleak-caches-by-default.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-disable-user-tracing-for-kmemleak-caches-by-default.patch
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------------------------------------------------------
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>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@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
@@ -1415,6 +1415,15 @@ 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;
@@ -1449,7 +1458,7 @@ 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,
_
Patches currently in -mm which might be from johannes.berg@xxxxxxxxx are
mm-slub-disable-user-tracing-for-kmemleak-caches-by-default.patch
