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man:slabinfo

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

NAME

     slabinfo - kernel slab allocator statistics

SYNOPSIS

     cat /proc/slabinfo

DESCRIPTION

     Frequently used objects in the Linux kernel (buffer heads, inodes, den-
     tries, etc.)  have their own cache.  The file /proc/slabinfo gives sta-
     tistics  on these caches.  The following (edited) output shows an exam-
     ple 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 for-
     mat.  (See VERSIONS, below.)  The next line lists the names of the col-
     umns 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:
     active_objs
            The  number of objects that are currently active (i.e., in use).
     num_objs
            The total number of allocated objects (i.e.,  objects  that  are
            both in use and not in use).
     objsize
            The size of objects in this slab, in bytes.
     objperslab
            The number of objects stored in each slab.
     pagesperslab
            The number of pages allocated for each slab.
     The  tunables entries in each line show tunable parameters for the cor-
     responding 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  tun-
     ables for a particular cache can be set by writing lines of the follow-
     ing 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 set-
     tings are left unchanged.
     The tunables entries in each line contain the following fields:
     limit  The maximum number of objects that will be cached.
     batchcount
            On SMP systems, this specifies the number of objects to transfer
            at one time when refilling the available object list.
     sharedfactor
            [To be documented]
     The slabdata entries in each line contain the following fields:
     active_slabs
            The number of active slabs.
     nums_slabs
            The total number of slabs.
     sharedavail
            [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.

VERSIONS

     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 dif-
     ferent 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
            series.
     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.

NOTES

     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.

SEE ALSO

     slabtop(1)
     The     kernel     source     file     Documentation/vm/slub.txt    and
     tools/vm/slabinfo.c.

COLOPHON

     This page is part of release 4.16 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/.
                                2017-09-15                       SLABINFO(5)
/data/webs/external/dokuwiki/data/pages/man/slabinfo.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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