Linux, performance analysis

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How to monitor resources and their usage

The availability of CPU and memory resources can be found in


and their usage can be monitored using


Users tend to care most about the %CPU time of top which is indeed important if many processes are asking for cpu-cycles.

But systems really get stalled by what is not reflected by %CPU: shortage of memory, causing the system to spend more time on exchanging memory with diskspace than actually running the jobs. This is indicated by vmstat as high values for

  • si so bi bo : exchanging memory
  • wa : waiting for I/O

The jobs with the highest amount of RESident memory contribute most to the memory exchange. They can be brought to the fore in top using the commands

F (Select sort field)
q (to be the Resident size)

If your desktop shows marks of memory shortage, consider reverting to a remote compute server. On those running Linux (most of them do), you may wish view only your own processes in top:

u (Show specific user only)

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