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 allo-
       cating 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 num-
       ber  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 3.25 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)