diff options
Diffstat (limited to 'man/man5/slabinfo.5')
| -rw-r--r-- | man/man5/slabinfo.5 | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/man/man5/slabinfo.5 b/man/man5/slabinfo.5 new file mode 100644 index 000000000..c3121fa28 --- /dev/null +++ b/man/man5/slabinfo.5 @@ -0,0 +1,220 @@ +.\" Copyright (c) 2001 Andreas Dilger (adilger@turbolinux.com) +.\" and Copyright (c) 2017 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH slabinfo 5 (date) "Linux man-pages (unreleased)" +.SH NAME +slabinfo \- kernel slab allocator statistics +.SH SYNOPSIS +.nf +.B cat /proc/slabinfo +.fi +.SH DESCRIPTION +Frequently used objects in the Linux kernel +(buffer heads, inodes, dentries, etc.) +have their own cache. +The file +.I /proc/slabinfo +gives statistics on these caches. +The following (edited) output shows an example of the +contents of this file: +.P +.EX +$ \fBsudo cat /proc/slabinfo\fP +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 +\&... +.EE +.P +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. +.P +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: +.IP \[bu] 3 +statistics +.IP \[bu] +tunables +.IP \[bu] +slabdata +.P +The statistics are as follows: +.TP +.I active_objs +The number of objects that are currently active (i.e., in use). +.TP +.I num_objs +The total number of allocated objects +(i.e., objects that are both in use and not in use). +.TP +.I objsize +The size of objects in this slab, in bytes. +.TP +.I objperslab +The number of objects stored in each slab. +.TP +.I pagesperslab +The number of pages allocated for each slab. +.P +The +.I tunables +entries in each line show tunable parameters for the corresponding cache. +When using the default SLUB allocator, there are no tunables, the +.I /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 +.IR /proc/slabinfo : +.P +.in +4n +.EX +# \fBecho \[aq]name limit batchcount sharedfactor\[aq] > /proc/slabinfo\fP +.EE +.in +.P +Here, +.I name +is the cache name, and +.IR limit , +.IR batchcount , +and +.I sharedfactor +are integers defining new values for the corresponding tunables. +The +.I limit +value should be a positive value, +.I batchcount +should be a positive value that is less than or equal to +.IR limit , +and +.I sharedfactor +should be nonnegative. +If any of the specified values is invalid, +the cache settings are left unchanged. +.P +The +.I tunables +entries in each line contain the following fields: +.TP +.I limit +The maximum number of objects that will be cached. +.\" https://lwn.net/Articles/56360/ +.\" This is the limit on the number of free objects that can be stored +.\" in the per-CPU free list for this slab cache. +.TP +.I batchcount +On SMP systems, this specifies the number of objects to transfer at one time +when refilling the available object list. +.\" https://lwn.net/Articles/56360/ +.\" On SMP systems, when we refill the available object list, instead +.\" of doing one object at a time, we do batch-count objects at a time. +.TP +.I sharedfactor +[To be documented] +.\" +.P +The +.I slabdata +entries in each line contain the following fields: +.TP +.I active_slabs +The number of active slabs. +.TP +.I nums_slabs +The total number of slabs. +.TP +.I sharedavail +[To be documented] +.P +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. +.P +Kernels configured with +.B 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. +.\" +.\" 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. +.SH VERSIONS +The +.I /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: +.TP +1.0 +Present throughout the Linux 2.2.x kernel series. +.TP +1.1 +Present in the Linux 2.4.x kernel series. +.\" First appeared in Linux 2.4.0-test3 +.TP +1.2 +A format that was briefly present in the Linux 2.5 development series. +.\" from Linux 2.5.45 to Linux 2.5.70 +.TP +2.0 +Present in Linux 2.6.x kernels up to and including Linux 2.6.9. +.\" First appeared in Linux 2.5.71 +.TP +2.1 +The current format, which first appeared in Linux 2.6.10. +.SH NOTES +Only root can read and (if the kernel was configured with +.BR CONFIG_SLAB ) +write the +.I /proc/slabinfo +file. +.P +The total amount of memory allocated to the SLAB/SLUB cache is shown in the +.I Slab +field of +.IR /proc/meminfo . +.SH SEE ALSO +.BR slabtop (1) +.P +The kernel source file +.I Documentation/vm/slub.txt +and +.IR tools/vm/slabinfo.c . |