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SLUB: support slub_debug on by default

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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>
This commit is contained in:
Christoph Lameter 2007-07-15 23:38:14 -07:00 committed by Linus Torvalds
parent fc9a07e7bf
commit f0630fff54
4 changed files with 88 additions and 46 deletions
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38
Documentation/kernel-parameters.txt
View File

@ -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]

2
Documentation/vm/slub.txt
View File

@ -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:

13
lib/Kconfig.debug
View File

@ -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

81
mm/slub.c
View File

@ -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;
}