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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 3.27 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)