Display Linux kernel slab cache information in real time

last updated in Categories Linux, Troubleshooting

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, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

1 comment

  1. Hello there,

    awesome tools, is there a way also to find out WHO is allocation the memory, i see a HUGE ammount of size-32 slaps growing over the weeks…

    Cheers,
    xuedi

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