NAME | SYNOPSIS | DESCRIPTION | FILES | VERSIONS | NOTES | COLOPHON

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

NAME         top

       slabinfo - kernel slab allocator statistics

SYNOPSIS         top

       cat /proc/slabinfo

DESCRIPTION         top

       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         top

       <linux/slab.h>

VERSIONS         top

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

NOTES         top

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

COLOPHON         top

       This page is part of release 4.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

                                 2007-09-30                      SLABINFO(5)