I understand that system load is kernel usage such as IO or network. If you don't believe you have high load of either of those two items, what would be some recommended steps to track down what is generating high system load? We are installing 'dstat' and will post results more load tests.

We are seeing the load under the column system% via sar. User load is normal, and the system is overall at about 50-70% CPU usage.

Thanks in advance

  • What does the output from top tell you? – Jenny D Oct 18 '14 at 20:33
  • 1
    Learn about and install monitoring. Gather metrics. Make decisions on facts. – user9517 Oct 18 '14 at 20:56

High load without high CPU usage is generally down to I/O, and mostly down to block devices (hard disks). Now, your programs may read/write heavily onto block device because they are not optimized, or because there's not enough memory in your system.

You can use cli program 'free' to see your memory consumption:

% free -otm
             total       used       free     shared    buffers     cached
Mem:         31728       2057      29670          0         65        733
Swap:            0          0          0
Total:       31728       2057      29670

If you're swapping, that could explain the load.

Next, you may use 'atop'. Atop is 'advanced top'. Start it with interval of 1 second (10 is default) and order processes by disk usage:

atop -D 1

Atop will color the bottleneck resource in red, so it will typically show you immediately what's causing the load.

  • We have dtrace installed now, and I will let you know if it is IO. There is zero IO wait, but we are also virtualized on VMware. – chrislovecnm Oct 19 '14 at 0:41

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