SLABINFO(5)						     Linux Programmer's Manual						       SLABINFO(5)

NAME

       /proc/slabinfo - kernel slab allocator statistics

SYNOPSIS

       cat /proc/slabinfo

DESCRIPTION

       Frequently  used  objects  in the Linux kernel (buffer heads, inodes, dentries, etc.)  have their own cache.  The file /proc/slabinfo gives
       statistics.  For example:

	   % cat /proc/slabinfo
	   slabinfo - version: 1.1
	   kmem_cache		 60	78    100    2	  2    1
	   blkdev_requests     5120   5120     96  128	128    1
	   mnt_cache		 20	40     96    1	  1    1
	   inode_cache	       7005  14792    480 1598 1849    1
	   dentry_cache        5469   5880    128  183	196    1
	   filp 		726    760     96   19	 19    1
	   buffer_head	      67131  71240     96 1776 1781    1
	   vm_area_struct      1204   1652     64   23	 28    1
	   ...
	   size-8192		  1	17   8192    1	 17    2
	   size-4096		 41	73   4096   41	 73    1
	   ...

       For each slab cache, the cache name, the number of currently active objects, the total number of available objects, the size of each object
       in  bytes,  the	number of pages with at least one active object, the total number of allocated pages, and the number of pages per slab are
       given.

       Note that because of object alignment and slab cache overhead, objects are not normally packed tightly into pages.  Pages with even one in-
       use object are considered in-use and cannot be freed.

       Kernels	compiled with slab cache statistics will also have "(statistics)" in the first line of output, and will have 5 additional columns,
       namely: the high water mark of active objects; the number of times objects have been allocated; the number of times  the  cache	has  grown
       (new  pages  added  to this cache); the number of times the cache has been reaped (unused pages removed from this cache); and the number of
       times there was an error allocating new pages to this cache.  If slab cache statistics are not enabled for this kernel, these columns  will
       not be shown.

       SMP  systems  will  also  have  "(SMP)" in the first line of output, and will have two additional columns for each slab, reporting the slab
       allocation policy for the CPU-local cache (to reduce the need for inter-CPU synchronization when allocating objects from the  cache).   The
       first  column  is  the per-CPU limit: the maximum number of objects that will be cached for each CPU.  The second column is the batchcount:
       the maximum number of free objects in the global cache that will be transferred to the per-CPU cache if it  is  empty,  or  the	number	of
       objects to be returned to the global cache if the per-CPU cache is full.

       If  both  slab  cache  statistics  and SMP are defined, there will be four additional columns, reporting the per-CPU cache statistics.  The
       first two are the per-CPU cache allocation hit and miss counts: the number of times an object was or was not available in the per-CPU cache
       for  allocation.   The  next  two are the per-CPU cache free hit and miss counts: the number of times a freed object could or could not fit
       within the per-CPU cache limit, before flushing objects to the global cache.

       It is possible to tune the SMP per-CPU slab cache limit and batchcount via:

	   echo "cache_name limit batchcount" > /proc/slabinfo

FILES

       <linux/slab.h>

VERSIONS

       /proc/slabinfo exists since Linux 2.1.23.  SMP per-CPU caches exist since Linux 2.4.0-test3.

NOTES

       Since Linux 2.6.16 the file /proc/slabinfo is only present if the CONFIG_SLAB kernel configuration option is enabled.

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

								    2007-09-30							       SLABINFO(5)