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I have a system whose load is rather high. As you can see from the top output below, CPU usage and I/O is negligible:

top - 17:31:59 up 4 days, 2:34, 2 users, load average: 1.00, 0.99, 1.00

Tasks: 71 total, 1 running, 70 sleeping, 0 stopped, 0 zombie

Cpu(s): 2.0%us, 2.0%sy, 0.0%ni, 95.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st

Mem: 960720k total, 707288k used, 253432k free,
67328k buffers

Swap: 2811896k total, 2644k used, 2809252k free, 528928k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

15310 root 20 0 2512 1128 888 R 2.1 0.1 0:00.05 top

I would appreciate any assistance with isolating the cause(s) of high load for when I/O and CPU are not factors.

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migrated from stackoverflow.com Feb 7 '11 at 18:23

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run "vmstat 1" and "mpstat 1" to gather more info please –  Ron Feb 7 '11 at 17:28
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0.70 is not a high load. What have you experienced that causes your view of a 'high load' on this server? –  MikeyB Feb 7 '11 at 18:51
    
vmstat procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- 0 0 2664 255272 67004 527560 0 0 0 0 315 224 0 0 100 0 0 0 2664 255272 67004 527560 0 0 0 0 320 230 0 1 99 0 0 0 2664 255264 67004 527560 0 0 0 0 322 223 0 0 100 0 mpstat 05:30:28 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle 05:30:29 PM all 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 05:30:30 PM all 0.00 0.00 0.00 0.00 0.99 0.00 0.00 0.00 99.01 –  devup Feb 15 '11 at 23:04
    
@Mikey Client does not like the fact that their legacy software solution used less than 0.80 load on the exact same hardware/OS setup. Long term, the new software brings their system's load to just under 3.00. No specific problem mentioned due to the high load, simply that they don't like the numbers they're seeing. Of note, the new software is a multi-threaded app running on 5+ year single core system. My main interest is grasping how the load can be above 1 when the CPU is idle, IO is dormant, and there remains plenty of memory? Thanks... –  devup Feb 15 '11 at 23:23
    
@MikeyB (please see previous comment) –  devup Feb 16 '11 at 1:30
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3 Answers

The high load can also be caused by a few factors:

  • processes in "uninterruptible sleep" (D in the process list), that's processes waiting for some I/O.
  • hardware issues, causing the system to wait for something (can be I/O).

Please check your process list (ps auxf), for any processes which may be in D state, or look weird.

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- There are no "D - Uninterruptible sleep" processes. - I see no indication that I/O is the culprit (top, vmstat, mpstat). –  devup Feb 15 '11 at 22:59
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Issue appears to be due to a known issue with Ubuntu 10.04 (Lucid).

Bug Reference

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do

iostat -xk
iotop

check the await column. Most likely that's the issue.

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