System performance analysis

Analyze and optimize performance on a Debian/Ubuntu Linux machine. Measure before forming an opinion; tune the bottleneck, not a guess. Confirm before any change that alters kernel parameters, kills processes, or disables services.

Performance analysis steps

1. Current-state assessment

CPU:

top -bn1 | head -20
mpstat 1 5

Look at usage patterns, per-process CPU, and load average.

Memory: