How to Fix High CPU Usage on Linux

What Causes This?

High CPU usage on Linux usually happens when one or more processes keep the processor busy for long periods. Common causes include runaway apps, background services, browser tabs, indexing jobs, package updates, and low available memory forcing the system to work harder. In some cases, old logs, cache files, and general system clutter can also contribute to slowdowns by increasing disk activity and making the whole system feel overloaded.

Common Symptoms

• Fans run loudly even when you are not doing much
• The system feels slow, laggy, or unresponsive
• Apps take a long time to open or switch between
• Battery drains faster than normal on a laptop
• One process in System Monitor or top stays near the top constantly

How to Fix It Manually

1. Find the process using the most CPU

   • Open a terminal.
   • Run:

     top

   • Look at the %CPU column to find the process using the most resources.
   • If you want a cleaner view, try:

     htop

     If htop is not installed, install it with your package manager first.

2. Stop or restart the problem app

   • If the high-CPU process is a normal app you opened, close it and see if CPU usage drops.
   • If it does not close properly, use:

     kill PID

     Replace PID with the process ID from top or htop.
   • If needed, force it:

     kill -9 PID

   • If the process is a service, restart it with:

     sudo systemctl restart service-name

3. Check startup apps and background services

   • Too many background programs can keep CPU usage high.
   • On systems with a desktop environment, open your Startup Applications tool and disable anything unnecessary.
   • To review running services, use:

     systemctl --type=service --state=running

   • Disable services you do not need only if you are sure what they do.

4. Install updates

   • Buggy software and outdated kernels can cause CPU spikes.
   • On Debian/Ubuntu-based systems, run:

     sudo apt update && sudo apt upgrade

   • On Fedora:

     sudo dnf upgrade

   • Reboot after updates if a kernel or major system package was installed.

5. Check memory and disk pressure

   • If RAM is full, the system may slow down and appear CPU-bound.
   • Check memory usage with:

     free -h

   • Check disk space with:

     df -h

   • Remove unnecessary files if your disk is nearly full.

6. Clean logs, cache, and temporary files

   • Large caches and leftover files can add unnecessary system load.
   • Clear package cache where appropriate. For example on Debian/Ubuntu:

     sudo apt clean

   • Review log size with:

     journalctl --disk-usage

   • Reduce old journal logs with:

     sudo journalctl --vacuum-time=7d

   • Be careful not to delete files manually unless you know they are safe to remove.

7. Scan for browser and extension issues

   • Web browsers are a common cause of high CPU usage on Linux.
   • Close extra tabs, disable heavy extensions, and check whether one site is causing the spike.
   • If CPU usage drops after closing the browser, the issue is likely tab, media, or extension related.

Fix It Automatically with Kudu

If you do not want to track down logs, caches, and clutter by hand, Kudu can do the cleanup automatically. It helps remove junk files that build up over time, freeing space and reducing the background load that can make a system feel slow.

Download Kudu Free →