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Commit f0630fff authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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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: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fc9a07e7

Documentation/kernel-parameters.txt

+21 −17
Original line number Diff line number Diff line
@@ -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]

Documentation/vm/slub.txt

+2 −0
Original line number Diff line number Diff line
@@ -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:

lib/Kconfig.debug

+13 −0
Original line number Diff line number Diff line
@@ -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

mm/slub.c

+51 −28
Original line number Diff line number Diff line
@@ -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;
@@ -888,28 +892,45 @@ static int free_debug_processing(struct kmem_cache *s, struct page *page, 


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' :

	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' : case 'Z' :

		case 'z':

			slub_debug |= SLAB_RED_ZONE;

			break;

			case 'p' : case 'P' :

		case 'p':

			slub_debug |= SLAB_POISON;

			break;

			case 'u' : case 'U' :

		case 'u':

			slub_debug |= SLAB_STORE_USER;

			break;

			case 't' : case 'T' :

		case 't':

			slub_debug |= SLAB_TRACE;

			break;

		default:
@@ -918,8 +939,10 @@ static int __init setup_slub_debug(char *str) 
		}

	}



check_slabs:

	if (*str == ',')

		slub_debug_slabs = str + 1;

out:

	return 1;

}