slabinfo

SLABINFO(5)			 Linux 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 "(statis-
       tics)" 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  batch-
       count:  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


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


FILES
       <linux/slab.h>



				  2001-06-19			  SLABINFO(5)