Linux, performance analysis

How to monitor resources and their usage

The availability of CPU and memory resources can be found in

/proc/cpuinfo
/proc/meminfo

and their usage can be monitored using

top
vmstat

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)
youraccount

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