USE method for resource checks

[snippet] 2026-09-29

USE method for resource checks

Brendan Gregg’s USE: Utilization, Saturation, Errors — ask all three for every resource.

For CPU / mem / disk / net / pools:

  Utilization  — how busy is it? (% busy, used/capacity)
  Saturation   — is work queued? (run queue, await, backlog)
  Errors       — is it failing? (retransmits, OOM, 5xx)

High util + low saturation  → busy but keeping up
High util + high saturation → bottleneck
Errors                     → fix correctness before tuning

Scenario: “Is the DB slow?” Check CPU USE, disk USE, connection-pool USE separately. Pool at 100% util with a wait queue (saturation) while disk is quiet usually means you’re connection-starved, not I/O-bound. Pair with RED (Rate, Errors, Duration) for the service view.