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NmonVersion12c

nmon version 12c for Linux Screen Shots

nmon for Linux Online screen shots

This is the start up screen when using nmon online

  • There are plenty of hints on how to switch on/off (toggle) the various stats and text graphs
  • The only one you have to remember if "q" to QUIT

This is the Help section

  • If you hit "h" you get this Help section with loads of hints. Hit "h" again to remove the Help

Resources section

  • Hit "r" for Resources to find out what nmon can discover about your processors and Linux OS version and other features
  • This is a bit of a weak area in Linux and vendors do this differently or not at all.
  • In this case we have SUSE SLES 10.2 running on four 4.2 GHz POWER6 CPUs

POWER LPAR details

  • This is Linux on Power running in a Logical Partition (LPAR) for this platform only we have LPAR details (hit "p")
  • We can see the LPAR is only consuming 0.004 of a single Power 6 Processor as it is just idling.

CPU Stats - Utilisation

  • Hit "c" for the CPU stats.
  • Here we see the four CPUs
  • I ran a load generator (nstress) to get the graphs active
  • "U" is user time, "s" is System time and "W" id waiting for Disk I/O time.
  • Obviously blank is used for idle time.

CPU Stats - again

  • This time the machine is busier
  • Note the ">" marks are the peak CPU usage - if you hit "0" (zero) these are reset to the far left.

CPU Long Term Graph

  • Hit "l" (lowercase L) to see these. "l" for long term
  • On peaky workloads like a web server you can drive yourself mad watching the above graph fluctuate up and down and guessing an average
  • This graph lets you see the last 70 snapshots and moves to the right. Once full it will wrap around.

CPU Long Term Graph - again

  • Note the top left now says 4 seconds - I slowed down the update and so snapshot rate of nmon to show a longer period of time.
  • Faster and Slower screen Updates - this works regardless of the stats you are watching:
    • Hit "-" to halve the time nmon pauses between updates of the screen i.e. if it is set to 2 seconds now you get updates once a second
    • Hit"+" to double the time nmon pauses between updates of the screen i.e. if it is set to 2 seconds now you get updates once in 4 seconds
    • You can't go below 1 second - nmon would take too much CPU time for that to make sense
    • Faster is good to watch for peaks
    • Slower is good to even out the peaks to see a stable average
  • Also note the "+" on the moving vertical bar - this shows the average number for the graphed data.

Memory Stats

  • Hit "m" for memory details
  • Note: this is a Power processor based system - there is no high memory as the Power processor has been 64 bit for a decade or more and these bizarre workaround to extend memory are not required.
  • We can see 15 MB of free RAM out of 484MB
  • And the paging space has not been used, yet!

Disk Graphs

  • Hit "d" for disk graphs
  • Note: that only sda = the actual disk gives us statistics and not the disk partitions sda1, sda2, etc.
  • This is, of course, a very small machine with just the one disk.
  • If we had lots more disk we may not be able to see them all.
  • Try making the font smaller and/or the window larger to show more lines
  • If you hit "." (dot) then only the busy disks are shown - this works on Top Processes too.

Disk Graphs - with workload

  • Here we see the disk is 23% busy and writing 19 MB/s
  • The graph shows "W" for Writing and "R" for Reading I/O

Disk Stats

  • Hit "D" for the Disks but this time the Numbers in more Detail.
  • We can see the numbers of transfers and block sizes etc.
  • Also we see the peak values - these can be reset to zero by hitting "0" (zero)

File Systems

  • Hit "j" for Journalling file systems - OK "f" would make more sense but that was used for something else in the past!
  • Here we see the root filesystem is 61% full

Network Stats

  • Hit "n"
  • All pretty obvious (I hope)

Network Stats - without error numbers

  • If you wait a few seconds and there are no errors the lower panel is switched off.
  • It will reappear is network error happen.
  • On some machines with a dozen networks this saves a lot of screen space

Network File System (NFS)

  • Hit "N"
  • OK this machine was not mounted or mounting NFS so the numbers are all zero.
  • Boring but I hope you get the idea.

Kernel Stats

  • Hit "k"
  • Linux does not have so may of these but we have the important once like Run Queue, Forks, Load average are not that useful as nmon already collects the detailed CPU stats and we have Uptime here too.

Disk Rain Diagram

  • Hit "o" (lowercase Oh!)
  • With just one disk this looks stupid (see the single "_" but imagine you had 640.
  • The panel would have 10 lines and one character per disk
  • As each disk gets busier more pixels are added to its character.
  • This gives you a quick idea of how busy your disks are, as a whole.
  • You also see unused disks or ranges of disks that are particularly busy.

Top Process Stats

  • Hit "t" to see the processes
  • Default mode is 3 and this arranges them in CPU use order.
  • You can see the big hitters are processes called "yes" and "ncpu" from the nstress tools

Top Processes in mode 1 = more details

  • Have the top Processes on screen (Hit "t") then hit "1" for mode 1
  • There are different stats shown including status, nice and priority

Top Processes in mode 4 = size order

  • Have the top Processes on screen (Hit "t") then hit "4" for mode 4
  • Here the processes are in memory size order
  • You can see the largest process in 504 MB and called "java" - no surprise there then!