Performance

OS performance troubleshooting on a live box: hunt down CPU, memory, I/O and process problems with top, vmstat, iostat and pidstat.

6 challenges · 0 easy · 5 medium · 1 pro

• Count the zombie processesmedium
  Several zombie (defunct) processes are lingering. Count how many there are and write the number to /home/player/answer.
• Find the disk under load (iostat)medium
  Sustained disk writes are hammering the box. Using iostat, identify the block DEVICE doing the most I/O and write its name (e.g. nvme0n1) to /home/player/answer.
• Pin down the CPU hog by PID (pidstat)medium
  Using pidstat, find the PID of the process using the most CPU and write just that number to /home/player/answer.
• Stop a CPU-pinning runawaymedium
  A runaway process is pinning a CPU core at ~100% and slowing the whole box. Track it down (its command name gives it away) and stop it.
• Stop a memory hogmedium
  Free memory has nearly run out — one process is hogging the RAM. Find it and stop it before the box starts swapping.
• Renice a greedy batch jobpro
  A legitimate batch job 'batch-encoder' is CPU-hungry and starving interactive work, but it must keep running. Lower its priority by renicing it to nice 19 — do NOT kill it.