Display Linux kernel slab cache information in real time

Posted on in Categories Linux, Troubleshooting last updated May 21, 2006

Linux has tons of frequently used objects in the kernel such as buffer heads, inodes, dentries, etc. and have their own cache. The file /proc/slabinfo (less /proc/slabinfo) gives statistics. It is possible that slab cache information can be used to debug kernel problems (see crash command man page for more info).

slabtop command displays detailed kernel slab cache information in real time. It displays a listing of the top caches sorted by one of the listed sort criteria. It also displays a statistics header filled with slab layer information.

It generates output like vmtop perl script but in real time:

$ vmtop

VMTOP output:

Memory:    750.6 Mb      Free:   2.2%    Buffers:  56.1%   Cached:   3.1%
                       Active:  69.3%   Inactive:  24.0%
Lowmem:    750.6 Mb      Free:   2.2%       Slab:   3.0%   Memmap:   0.0%
                       Stacks:   0.1%       PMDs:   0.0%     PTEs:   0.3%

Top slabs:
      size-131072(dma)       0.1 Mb  (Active:      0.0 Mb,   0.0% full)
           size-131072       0.1 Mb  (Active:      0.0 Mb,   0.0% full)
       size-65536(dma)       0.1 Mb  (Active:      0.0 Mb,   0.0% full)
            size-65536       0.1 Mb  (Active:      0.0 Mb, 100.0% full)
       size-32768(dma)       0.0 Mb  (Active:      0.0 Mb,   0.0% full)

Now let us see output of slabtop command:

$ slabtop

slabtop command output:

slabtop command output
(Click to enlarge)

See also:

  • Read man page of slabtop for SORT CRITERIA related information (the default sort criteria is to sort by the number of objects).

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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