Documentation/ABI/testing/sysfs-kernel-slab

What:		/sys/kernel/slab
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The /sys/kernel/slab directory contains a snapshot of the
		internal state of the SLUB allocator for each cache.  Certain
		files may be modified to change the behavior of the cache (and
		any cache it aliases, if any).
Users:		kernel memory tuning tools

What:		/sys/kernel/slab/cache/aliases
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The aliases file is read-only and specifies how many caches
		have merged into this cache.

What:		/sys/kernel/slab/cache/align
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The align file is read-only and specifies the cache's object
		alignment in bytes.

What:		/sys/kernel/slab/cache/alloc_calls
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_calls file is read-only and lists the kernel code
		locations from which allocations for this cache were performed.
		The alloc_calls file only contains information if debugging is
		enabled for that cache (see Documentation/vm/slub.txt).

What:		/sys/kernel/slab/cache/alloc_fastpath
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_fastpath file is read-only and specifies how many
		objects have been allocated using the fast path.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/alloc_from_partial
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_from_partial file is read-only and specifies how
		many times a cpu slab has been full and it has been refilled
		by using a slab from the list of partially used slabs.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/alloc_refill
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_refill file is read-only and specifies how many
		times the per-cpu freelist was empty but there were objects
		available as the result of remote cpu frees.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/alloc_slab
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_slab file is read-only and specifies how many times
		a new slab had to be allocated from the page allocator.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/alloc_slowpath
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The alloc_slowpath file is read-only and specifies how many
		objects have been allocated using the slow path because of a
		refill or allocation from a partial or new slab.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/cache_dma
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The cache_dma file is read-only and specifies whether objects
		are from ZONE_DMA.
		Available when CONFIG_ZONE_DMA is enabled.

What:		/sys/kernel/slab/cache/cpu_slabs
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The cpu_slabs file is read-only and displays how many cpu slabs
		are active and their NUMA locality.

What:		/sys/kernel/slab/cache/cpuslab_flush
Date:		April 2009
KernelVersion:	2.6.31
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file cpuslab_flush is read-only and specifies how many
		times a cache's cpu slabs have been flushed as the result of
		destroying or shrinking a cache, a cpu going offline, or as
		the result of forcing an allocation from a certain node.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/ctor
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The ctor file is read-only and specifies the cache's object
		constructor function, which is invoked for each object when a
		new slab is allocated.

What:		/sys/kernel/slab/cache/deactivate_empty
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file deactivate_empty is read-only and specifies how many
		times an empty cpu slab was deactivated.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/deactivate_full
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file deactivate_full is read-only and specifies how many
		times a full cpu slab was deactivated.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/deactivate_remote_frees
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file deactivate_remote_frees is read-only and specifies how
		many times a cpu slab has been deactivated and contained free
		objects that were freed remotely.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/deactivate_to_head
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file deactivate_to_head is read-only and specifies how
		many times a partial cpu slab was deactivated and added to the
		head of its node's partial list.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/deactivate_to_tail
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file deactivate_to_tail is read-only and specifies how
		many times a partial cpu slab was deactivated and added to the
		tail of its node's partial list.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/destroy_by_rcu
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The destroy_by_rcu file is read-only and specifies whether
		slabs (not objects) are freed by rcu.

What:		/sys/kernel/slab/cache/free_add_partial
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file free_add_partial is read-only and specifies how many
		times an object has been freed in a full slab so that it had to
		added to its node's partial list.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/free_calls
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The free_calls file is read-only and lists the locations of
		object frees if slab debugging is enabled (see
		Documentation/vm/slub.txt).

What:		/sys/kernel/slab/cache/free_fastpath
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The free_fastpath file is read-only and specifies how many
		objects have been freed using the fast path because it was an
		object from the cpu slab.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/free_frozen
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The free_frozen file is read-only and specifies how many
		objects have been freed to a frozen slab (i.e. a remote cpu
		slab).
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/free_remove_partial
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file free_remove_partial is read-only and specifies how
		many times an object has been freed to a now-empty slab so
		that it had to be removed from its node's partial list.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/free_slab
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The free_slab file is read-only and specifies how many times an
		empty slab has been freed back to the page allocator.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/free_slowpath
Date:		February 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The free_slowpath file is read-only and specifies how many
		objects have been freed using the slow path (i.e. to a full or
		partial slab).
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/hwcache_align
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The hwcache_align file is read-only and specifies whether
		objects are aligned on cachelines.

What:		/sys/kernel/slab/cache/min_partial
Date:		February 2009
KernelVersion:	2.6.30
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		David Rientjes <rientjes@google.com>
Description:
		The min_partial file specifies how many empty slabs shall
		remain on a node's partial list to avoid the overhead of
		allocating new slabs.  Such slabs may be reclaimed by utilizing
		the shrink file.

What:		/sys/kernel/slab/cache/object_size
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The object_size file is read-only and specifies the cache's
		object size.

What:		/sys/kernel/slab/cache/objects
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The objects file is read-only and displays how many objects are
		active and from which nodes they are from.

What:		/sys/kernel/slab/cache/objects_partial
Date:		April 2008
KernelVersion:	2.6.26
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The objects_partial file is read-only and displays how many
		objects are on partial slabs and from which nodes they are
		from.

What:		/sys/kernel/slab/cache/objs_per_slab
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file objs_per_slab is read-only and specifies how many
		objects may be allocated from a single slab of the order
		specified in /sys/kernel/slab/cache/order.

What:		/sys/kernel/slab/cache/order
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The order file specifies the page order at which new slabs are
		allocated.  It is writable and can be changed to increase the
		number of objects per slab.  If a slab cannot be allocated
		because of fragmentation, SLUB will retry with the minimum order
		possible depending on its characteristics.

What:		/sys/kernel/slab/cache/order_fallback
Date:		April 2008
KernelVersion:	2.6.26
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file order_fallback is read-only and specifies how many
		times an allocation of a new slab has not been possible at the
		cache's order and instead fallen back to its minimum possible
		order.
		Available when CONFIG_SLUB_STATS is enabled.

What:		/sys/kernel/slab/cache/partial
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The partial file is read-only and displays how long many
		partial slabs there are and how long each node's list is.

What:		/sys/kernel/slab/cache/poison
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The poison file specifies whether objects should be poisoned
		when a new slab is allocated.

What:		/sys/kernel/slab/cache/reclaim_account
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The reclaim_account file specifies whether the cache's objects
		are reclaimable (and grouped by their mobility).

What:		/sys/kernel/slab/cache/red_zone
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The red_zone file specifies whether the cache's objects are red
		zoned.

What:		/sys/kernel/slab/cache/remote_node_defrag_ratio
Date:		January 2008
KernelVersion:	2.6.25
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The file remote_node_defrag_ratio specifies the percentage of
		times SLUB will attempt to refill the cpu slab with a partial
		slab from a remote node as opposed to allocating a new slab on
		the local node.  This reduces the amount of wasted memory over
		the entire system but can be expensive.
		Available when CONFIG_NUMA is enabled.

What:		/sys/kernel/slab/cache/sanity_checks
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The sanity_checks file specifies whether expensive checks
		should be performed on free and, at minimum, enables double free
		checks.  Caches that enable sanity_checks cannot be merged with
		caches that do not.

What:		/sys/kernel/slab/cache/shrink
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The shrink file is written when memory should be reclaimed from
		a cache.  Empty partial slabs are freed and the partial list is
		sorted so the slabs with the fewest available objects are used
		first.

What:		/sys/kernel/slab/cache/slab_size
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The slab_size file is read-only and specifies the object size
		with metadata (debugging information and alignment) in bytes.

What:		/sys/kernel/slab/cache/slabs
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The slabs file is read-only and displays how long many slabs
		there are (both cpu and partial) and from which nodes they are
		from.

What:		/sys/kernel/slab/cache/store_user
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The store_user file specifies whether the location of
		allocation or free should be tracked for a cache.

What:		/sys/kernel/slab/cache/total_objects
Date:		April 2008
KernelVersion:	2.6.26
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The total_objects file is read-only and displays how many total
		objects a cache has and from which nodes they are from.

What:		/sys/kernel/slab/cache/trace
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		The trace file specifies whether object allocations and frees
		should be traced.

What:		/sys/kernel/slab/cache/validate
Date:		May 2007
KernelVersion:	2.6.22
Contact:	Pekka Enberg <penberg@cs.helsinki.fi>,
		Christoph Lameter <cl@linux-foundation.org>
Description:
		Writing to the validate file causes SLUB to traverse all of its
		cache's objects and check the validity of metadata.