5.2.26. /proc/slabinfo

This file gives full information about memory usage on the slab level. Linux kernels greater than version 2.2 use slab pools to manage memory above the page level. Commonly used objects have their own slab pools.
Instead of parsing the highly verbose /proc/slabinfo file manually, the /usr/bin/slabtop program displays kernel slab cache information in real time. This program allows for custom configurations, including column sorting and screen refreshing.
A sample screen shot of /usr/bin/slabtop usually looks like the following example:
 Active / Total Objects (% used)    : 133629 / 147300 (90.7%)
 Active / Total Slabs (% used)      : 11492 / 11493 (100.0%)
 Active / Total Caches (% used)     : 77 / 121 (63.6%)
 Active / Total Size (% used)       : 41739.83K / 44081.89K (94.7%)
 Minimum / Average / Maximum Object : 0.01K / 0.30K / 128.00K
                                                                                                                  
  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
 44814  43159  96%    0.62K   7469        6     29876K ext3_inode_cache
 36900  34614  93%    0.05K    492       75      1968K buffer_head
 35213  33124  94%    0.16K   1531       23      6124K dentry_cache
  7364   6463  87%    0.27K    526       14      2104K radix_tree_node
  2585   1781  68%    0.08K     55       47       220K vm_area_struct
  2263   2116  93%    0.12K     73       31       292K size-128
  1904   1125  59%    0.03K     16      119        64K size-32
  1666    768  46%    0.03K     14      119        56K anon_vma
  1512   1482  98%    0.44K    168        9       672K inode_cache
  1464   1040  71%    0.06K     24       61        96K size-64
  1320    820  62%    0.19K     66       20       264K filp
   678    587  86%    0.02K      3      226        12K dm_io
   678    587  86%    0.02K      3      226        12K dm_tio
   576    574  99%    0.47K     72        8       288K proc_inode_cache
   528    514  97%    0.50K     66        8       264K size-512
   492    372  75%    0.09K     12       41        48K bio
   465    314  67%    0.25K     31       15       124K size-256
   452    331  73%    0.02K      2      226         8K biovec-1
   420    420 100%    0.19K     21       20        84K skbuff_head_cache
   305    256  83%    0.06K      5       61        20K biovec-4
   290      4   1%    0.01K      1      290         4K revoke_table
   264    264 100%    4.00K    264        1      1056K size-4096
   260    256  98%    0.19K     13       20        52K biovec-16
   260    256  98%    0.75K     52        5       208K biovec-64
Some of the more commonly used statistics in /proc/slabinfo that are included into /usr/bin/slabtop include:
  • OBJS — The total number of objects (memory blocks), including those in use (allocated), and some spares not in use.
  • ACTIVE — The number of objects (memory blocks) that are in use (allocated).
  • USE — Percentage of total objects that are active. ((ACTIVE/OBJS)(100))
  • OBJ SIZE — The size of the objects.
  • SLABS — The total number of slabs.
  • OBJ/SLAB — The number of objects that fit into a slab.
  • CACHE SIZE — The cache size of the slab.
  • NAME — The name of the slab.
For more information on the /usr/bin/slabtop program, refer to the slabtop man page.