Why 'checking CPU usage' means more than one thing

When your Mac feels hot, your fans spin up, or an app suddenly feels sluggish, the first question is always the same: what's actually using my system's resources right now? On a Mac there are really three ways to answer that, and each fits a different situation - a one-time check, a deep terminal dig, or an always-on glance you keep for the rest of the day.

Method 1: Activity Monitor (built-in, best for a one-time check)

Activity Monitor is the fastest way to answer the question once:

  1. Open Spotlight (Cmd+Space) and type Activity Monitor
  2. Click the CPU tab to sort processes by CPU %
  3. Switch to the Memory, Energy, Disk, or Network tabs for those metrics
  4. Double-click any process for a live mini-graph

The catch: Activity Monitor only shows you the picture at the moment you open it. Close it, and you lose visibility - which is exactly when a background process likes to spike again.

Method 2: Terminal (best for scripting or SSH sessions)

Power users can pull the same numbers from the command line:

top -o cpu          # live CPU-sorted process list
top -o mem          # live memory-sorted process list
sudo powermetrics --samplers gpu_power -i 1000   # GPU utilization

This is powerful but not something you want running in a visible window all day, and powermetrics needs sudo, which isn't practical for a quick glance.

Method 3: A live menu bar monitor (best for ongoing awareness)

For everyday use, the most practical option is a small, persistent readout that lives in your menu bar - no app to open, no window to lose, just a glance whenever you want one. This is what DustByte's System Monitor is built for.

System Monitor adds up to six independent, opt-in menu bar items, each tracking one metric:

  • CPU - overall load plus a User/System split
  • GPU - overall utilization, with a Renderer/Tiler split on supported Macs
  • Memory - live RAM usage and pressure
  • Disk - read/write throughput and operations
  • Network - live download/upload speed, plus a running daily and monthly usage tracker
  • Battery - charge level and status

Every enabled metric refreshes once per second - the same rate Activity Monitor uses - and clicking its menu bar icon opens a small popover with the live number and a short rolling graph, so you can see whether a spike is a one-off or a sustained climb.

Turning it on

  1. Open DustByte and go to Settings
  2. Select the Monitoring tab
  3. Toggle on whichever metrics you want to track - each one adds its own icon to your menu bar immediately
  4. Click any icon to see the live value and graph

See the full walkthrough in our System Monitor tutorial.

Which metric should you actually keep on?

You don't need all six running at once. A practical starting point:

  • Laptop users worried about battery: keep Battery and CPU on
  • Video editors or gamers: keep GPU and Memory on
  • Anyone on a metered or capped connection: keep Network on to track daily/monthly data
  • Developers with heavy builds: keep CPU and Disk on to catch I/O bottlenecks

Network keeps tracking your daily/monthly usage totals in the background even with its menu bar icon switched off, so you never lose that running total just because you tidied up your menu bar.

A quick comparison

  • Activity Monitor: free, built-in, but only useful while the window is open
  • Terminal (top/powermetrics): free, scriptable, but not practical for casual glancing
  • Menu bar monitor (System Monitor): always visible, near-zero effort to check, and only samples the metrics you actually enable

Conclusion

If you only ever need a snapshot, Activity Monitor is fine. But if you want to actually notice when your Mac starts working harder than it should - before the fans give it away - a menu bar monitor that's already running beats reopening an app every time. DustByte's System Monitor is included with every DustByte plan and is fully unlimited during the 7-day free trial.