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

       slabinfo - kernel slab allocator statistics

       cat /proc/slabinfo

       Frequently used objects in the Linux kernel (buffer heads, inodes,
       dentries, etc.)  have their own cache.  The file /proc/slabinfo gives
       statistics on these caches.  The following (edited) output shows an
       example of the contents of this file:

       $ sudo cat /proc/slabinfo
       slabinfo - version: 2.1
       # name    <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> ...
       sigqueue      100  100  160   25  1 : tunables  0  0  0 : slabdata   4   4  0
       sighand_cache 355   405 2112  15  8 : tunables  0  0  0 : slabdata  27  27  0
       kmalloc-8192   96   96  8192   4  8 : tunables  0  0  0 : slabdata  24  24  0

       The first line of output includes a version number, which allows an
       application that is reading the file to handle changes in the file
       format.  (See VERSIONS, below.)  The next line lists the names of the
       columns in the remaining lines.

       Each of the remaining lines displays information about a specified cache.
       Following the cache name, the output shown in each line shows three
       components for each cache:

       *  statistics

       *  tunables

       *  slabdata

       The statistics are as follows:

              The number of objects that are currently active (i.e., in use).

              The total number of allocated objects (i.e., objects that are both
              in use and not in use).

              The size of objects in this slab, in bytes.

              The number of objects stored in each slab.

              The number of pages allocated for each slab.

       The tunables entries in each line show tunable parameters for the
       corresponding cache.  When using the default SLUB allocator, there are no
       tunables, the /proc/slabinfo file is not writable, and the value 0 is
       shown in these fields.  When using the older SLAB allocator, the tunables
       for a particular cache can be set by writing lines of the following form
       to /proc/slabinfo:

           # echo 'name limit batchcount sharedfactor' > /proc/slabinfo

       Here, name is the cache name, and limit, batchcount, and sharedfactor are
       integers defining new values for the corresponding tunables.  The limit
       value should be a positive value, batchcount should be a positive value
       that is less than or equal to limit, and sharedfactor should be
       nonnegative.  If any of the specified values is invalid, the cache
       settings are left unchanged.

       The tunables entries in each line contain the following fields:

       limit  The maximum number of objects that will be cached.

              On SMP systems, this specifies the number of objects to transfer
              at one time when refilling the available object list.

              [To be documented]

       The slabdata entries in each line contain the following fields:

              The number of active slabs.

              The total number of slabs.

              [To be documented]

       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 configured with CONFIG_DEBUG_SLAB will also have additional
       statistics fields in each line, and the first line of the file will
       contain the string "(statistics)".  The statistics field include : 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.

       The /proc/slabinfo file first appeared in Linux 2.1.23.  The file is
       versioned, and over time there have been a number of versions with
       different layouts:

       1.0    Present throughout the Linux 2.2.x kernel series.

       1.1    Present in the Linux 2.4.x kernel series.

       1.2    A format that was briefly present in the Linux 2.5 development

       2.0    Present in Linux 2.6.x kernels up to and including Linux 2.6.9.

       2.1    The current format, which first appeared in Linux 2.6.10.

       Only root can read and (if the kernel was configured with CONFIG_SLAB)
       write the /proc/slabinfo file.

       The total amount of memory allocated to the SLAB/SLUB cache is shown in
       the Slab field of /proc/meminfo.


       The kernel source file Documentation/vm/slub.txt and tools/vm/slabinfo.c.

       This page is part of release 5.12 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

                                   2021-03-22                        SLABINFO(5)