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authorChristoph Lameter <clameter@sgi.com>2007-07-15 23:38:14 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:36 -0700
commitf0630fff54a239efbbd89faf6a62da071ef1ff78 (patch)
tree4004adc3adf4dbe1a6188ca0bbd56f7606d4d05f
parentfc9a07e7bf1a76e710f5df017abb07628db1781d (diff)
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SLUB: support slub_debug on by default
Add a new configuration variable CONFIG_SLUB_DEBUG_ON If set then the kernel will be booted by default with slab debugging switched on. Similar to CONFIG_SLAB_DEBUG. By default slab debugging is available but must be enabled by specifying "slub_debug" as a kernel parameter. Also add support to switch off slab debugging for a kernel that was built with CONFIG_SLUB_DEBUG_ON. This works by specifying slub_debug=- as a kernel parameter. Dave Jones wanted this feature. http://marc.info/?l=linux-kernel&m=118072189913045&w=2 [akpm@linux-foundation.org: clean up switch statement] Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/kernel-parameters.txt38
-rw-r--r--Documentation/vm/slub.txt2
-rw-r--r--lib/Kconfig.debug13
-rw-r--r--mm/slub.c79
4 files changed, 87 insertions, 45 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4344f69ae24..8916410307f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1580,35 +1580,39 @@ and is between 256 and 4096 characters. It is defined in the file
slram= [HW,MTD]
- slub_debug [MM, SLUB]
- Enabling slub_debug allows one to determine the culprit
- if slab objects become corrupted. Enabling slub_debug
- creates guard zones around objects and poisons objects
- when not in use. Also tracks the last alloc / free.
- For more information see Documentation/vm/slub.txt.
+ slub_debug[=options[,slabs]] [MM, SLUB]
+ Enabling slub_debug allows one to determine the
+ culprit if slab objects become corrupted. Enabling
+ slub_debug can create guard zones around objects and
+ may poison objects when not in use. Also tracks the
+ last alloc / free. For more information see
+ Documentation/vm/slub.txt.
slub_max_order= [MM, SLUB]
- Determines the maximum allowed order for slabs. Setting
- this too high may cause fragmentation.
- For more information see Documentation/vm/slub.txt.
+ Determines the maximum allowed order for slabs.
+ A high setting may cause OOMs due to memory
+ fragmentation. For more information see
+ Documentation/vm/slub.txt.
slub_min_objects= [MM, SLUB]
- The minimum objects per slab. SLUB will increase the
- slab order up to slub_max_order to generate a
- sufficiently big slab to satisfy the number of objects.
- The higher the number of objects the smaller the overhead
- of tracking slabs.
+ The minimum number of objects per slab. SLUB will
+ increase the slab order up to slub_max_order to
+ generate a sufficiently large slab able to contain
+ the number of objects indicated. The higher the number
+ of objects the smaller the overhead of tracking slabs
+ and the less frequently locks need to be acquired.
For more information see Documentation/vm/slub.txt.
slub_min_order= [MM, SLUB]
Determines the mininum page order for slabs. Must be
- lower than slub_max_order
+ lower than slub_max_order.
For more information see Documentation/vm/slub.txt.
slub_nomerge [MM, SLUB]
- Disable merging of slabs of similar size. May be
+ Disable merging of slabs with similar size. May be
necessary if there is some reason to distinguish
- allocs to different slabs.
+ allocs to different slabs. Debug options disable
+ merging on their own.
For more information see Documentation/vm/slub.txt.
smart2= [HW]
diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt
index 1523320abd8..df812b03b65 100644
--- a/Documentation/vm/slub.txt
+++ b/Documentation/vm/slub.txt
@@ -41,6 +41,8 @@ Possible debug options are
P Poisoning (object and padding)
U User tracking (free and alloc)
T Trace (please only use on single slabs)
+ - Switch all debugging off (useful if the kernel is
+ configured with CONFIG_SLUB_DEBUG_ON)
F.e. in order to boot just with sanity checks and red zoning one would specify:
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index fab32a28637..640844024ff 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -152,6 +152,19 @@ config DEBUG_SLAB_LEAK
bool "Memory leak debugging"
depends on DEBUG_SLAB
+config SLUB_DEBUG_ON
+ bool "SLUB debugging on by default"
+ depends on SLUB && SLUB_DEBUG
+ default n
+ help
+ Boot with debugging on by default. SLUB boots by default with
+ the runtime debug capabilities switched off. Enabling this is
+ equivalent to specifying the "slub_debug" parameter on boot.
+ There is no support for more fine grained debug control like
+ possible with slub_debug=xxx. SLUB debugging may be switched
+ off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
+ "slub_debug=-".
+
config DEBUG_PREEMPT
bool "Debug preemptible kernel"
depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
diff --git a/mm/slub.c b/mm/slub.c
index e0cf6213abc..6aea48942c2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -323,7 +323,11 @@ static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
/*
* Debug settings:
*/
+#ifdef CONFIG_SLUB_DEBUG_ON
+static int slub_debug = DEBUG_DEFAULT_FLAGS;
+#else
static int slub_debug;
+#endif
static char *slub_debug_slabs;
@@ -888,38 +892,57 @@ fail:
static int __init setup_slub_debug(char *str)
{
- if (!str || *str != '=')
- slub_debug = DEBUG_DEFAULT_FLAGS;
- else {
- str++;
- if (*str == 0 || *str == ',')
- slub_debug = DEBUG_DEFAULT_FLAGS;
- else
- for( ;*str && *str != ','; str++)
- switch (*str) {
- case 'f' : case 'F' :
- slub_debug |= SLAB_DEBUG_FREE;
- break;
- case 'z' : case 'Z' :
- slub_debug |= SLAB_RED_ZONE;
- break;
- case 'p' : case 'P' :
- slub_debug |= SLAB_POISON;
- break;
- case 'u' : case 'U' :
- slub_debug |= SLAB_STORE_USER;
- break;
- case 't' : case 'T' :
- slub_debug |= SLAB_TRACE;
- break;
- default:
- printk(KERN_ERR "slub_debug option '%c' "
- "unknown. skipped\n",*str);
- }
+ slub_debug = DEBUG_DEFAULT_FLAGS;
+ if (*str++ != '=' || !*str)
+ /*
+ * No options specified. Switch on full debugging.
+ */
+ goto out;
+
+ if (*str == ',')
+ /*
+ * No options but restriction on slabs. This means full
+ * debugging for slabs matching a pattern.
+ */
+ goto check_slabs;
+
+ slub_debug = 0;
+ if (*str == '-')
+ /*
+ * Switch off all debugging measures.
+ */
+ goto out;
+
+ /*
+ * Determine which debug features should be switched on
+ */
+ for ( ;*str && *str != ','; str++) {
+ switch (tolower(*str)) {
+ case 'f':
+ slub_debug |= SLAB_DEBUG_FREE;
+ break;
+ case 'z':
+ slub_debug |= SLAB_RED_ZONE;
+ break;
+ case 'p':
+ slub_debug |= SLAB_POISON;
+ break;
+ case 'u':
+ slub_debug |= SLAB_STORE_USER;
+ break;
+ case 't':
+ slub_debug |= SLAB_TRACE;
+ break;
+ default:
+ printk(KERN_ERR "slub_debug option '%c' "
+ "unknown. skipped\n",*str);
+ }
}
+check_slabs:
if (*str == ',')
slub_debug_slabs = str + 1;
+out:
return 1;
}