lkml.org 
[lkml]   [2019]   [Apr]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC 1/2] mm, slub: introduce static key for slub_debug
Date
One advantage of CONFIG_SLUB_DEBUG is that a generic distro kernel can be built
with it, but it's inactive until enabled on boot or at runtime, without
rebuilding the kernel. With a static key, we can minimize the overhead of
checking whether slub_debug is enabled, as we do for e.g. page_owner.

For now and for simplicity, the static key stays enabled for the whole uptime
once activated for any cache, although some per-cache debugging options can be
also disabled at runtime. This can be improved if there's interest.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index d30ede89f4a6..398e53e16e2e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -115,10 +115,21 @@
* the fast path and disables lockless freelists.
*/

+#ifdef CONFIG_SLUB_DEBUG
+#ifdef CONFIG_SLUB_DEBUG_ON
+DEFINE_STATIC_KEY_TRUE(slub_debug_enabled);
+#else
+DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
+#endif
+#endif
+
static inline int kmem_cache_debug(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_DEBUG
- return unlikely(s->flags & SLAB_DEBUG_FLAGS);
+ if (static_branch_unlikely(&slub_debug_enabled))
+ return s->flags & SLAB_DEBUG_FLAGS;
+ else
+ return 0;
#else
return 0;
#endif
@@ -1287,6 +1298,9 @@ static int __init setup_slub_debug(char *str)
if (*str == ',')
slub_debug_slabs = str + 1;
out:
+ if (slub_debug)
+ static_branch_enable(&slub_debug_enabled);
+
return 1;
}

@@ -5193,6 +5207,7 @@ static ssize_t red_zone_store(struct kmem_cache *s,
s->flags &= ~SLAB_RED_ZONE;
if (buf[0] == '1') {
s->flags |= SLAB_RED_ZONE;
+ static_branch_enable(&slub_debug_enabled);
}
calculate_sizes(s, -1);
return length;
@@ -5213,6 +5228,7 @@ static ssize_t poison_store(struct kmem_cache *s,
s->flags &= ~SLAB_POISON;
if (buf[0] == '1') {
s->flags |= SLAB_POISON;
+ static_branch_enable(&slub_debug_enabled);
}
calculate_sizes(s, -1);
return length;
@@ -5234,6 +5250,7 @@ static ssize_t store_user_store(struct kmem_cache *s,
if (buf[0] == '1') {
s->flags &= ~__CMPXCHG_DOUBLE;
s->flags |= SLAB_STORE_USER;
+ static_branch_enable(&slub_debug_enabled);
}
calculate_sizes(s, -1);
return length;
--
2.21.0
\
 
 \ /
  Last update: 2019-04-04 11:16    [W:0.091 / U:16.048 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site