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slabtop

slabtop

This document summarizes the usage of slabtop, which displays slab usage.

1. slabtop

1.1. slabtop (-s o) 

$ slabtop
 Active / Total Objects (% used)    : 3108938 / 3354154 (92.7%)
 Active / Total Slabs (% used)      : 118963 / 118963 (100.0%)
 Active / Total Caches (% used)     : 86 / 124 (69.4%)
 Active / Total Size (% used)       : 892011.17K / 929895.83K (95.9%)
 Minimum / Average / Maximum Object : 0.01K / 0.28K / 8.00K

  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
703560 518344   0%    0.10K  18040       39     72160K buffer_head
590793 560567   0%    0.19K  28133       21    112532K dentry
533970 529404   0%    0.04K   5235      102     20940K ext4_extent_status
461160 456150   0%    1.06K  30744       15    491904K ext4_inode_cache
274200 272799   0%    0.13K   9140       30     36560K kernfs_node_cache
213952 212839   0%    0.06K   3343       64     13372K kmalloc-64
113610 111480   0%    0.09K   2705       42     10820K kmalloc-96
 86744  80971   0%    0.57K   6196       14     49568K radix_tree_node
 77454  76476   0%    0.59K   5958       13     47664K inode_cache
 52480  51713   0%    0.12K   1640       32      6560K kmalloc-128
 49408  48879   0%    0.03K    386      128      1544K kmalloc-32
 20736  20736 100%    0.02K     81      256       324K kmalloc-16
 20096  17863   0%    0.06K    314       64      1256K pid
 18636  18316   0%    0.66K   1553       12     12424K proc_inode_cache
 14122  14122 100%    0.67K    614       23      9824K ovl_inode
 11172  10774   0%    0.20K    588       19      2352K vm_area_struct
 10626  10304   0%    0.09K    231       46       924K anon_vma
  9456   8372   0%    0.25K    591       16      2364K filp
  8740   8740 100%    0.81K    460       19      7360K fuse_inode
  8192   8192 100%    0.01K     16      512        64K kmalloc-8
[Shell 1] slabtop

Displays slab usage sorted by number of slab objects in descending order. [Shell 1] shows the output of slabtop displaying slab usage sorted by number of slab objects in descending order. In [Shell 1], each column has the following meaning:

  • OBJS : Total number of slab objects
  • ACTIVE : Number of slab objects in active state
  • USE : Cache utilization rate
  • OBJ SIZE : Size of slab object
  • SLABS : Number of slabs
  • OBJ/SLAB : Number of slab objects per slab
  • CACHE SIZE : Size of cache
  • NAME : Name of cache

A cache consists of multiple slabs, and each slab consists of a collection of slab objects. Each slab has a page size. Since page size is generally 4KB, the following formulas hold:

  • 4KB * SLABS = CACHE SIZE
  • OBJ/SLAB * OBJ SIZE < 4KB

1.2. slabtop [-s a|b|c|l|v|n|p|s|u ]

Outputs slab usage sorted by specific criteria. Criteria are as follows:

  • a : ACTIVE
  • b : OBJ/SLAB
  • c : CACHE SIZE
  • l : SLABS
  • v : Number of active slabs
  • n : NAME
  • p : Number of slabs per page
  • s : OBJ SIZE
  • u : USE

2. References

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