Fix High CPU Usage on a Linux VPS

Signs of high CPU use

• CPU stays above 80-90% for a long time.
• The load average is higher than the number of CPU cores.
• SSH is slow.
• Your website is slow.

Check the load average:

uptime

Solution 1: Find the process

top shows live use:

top

Press P to sort by CPU. Press q to quit.

htop is easier to read:

sudo apt install htop -y

htop

Solution 2: Stop or restart the cause

Stop one process (use the PID from top):

sudo kill -9 PID

Try sudo kill PID first. It lets the program close in a clean way.

Restart a service

sudo systemctl restart apache2

sudo systemctl restart nginx

Solution 3: Tune the web server

Apache

sudo nano /etc/apache2/apache2.conf

Add or change:

KeepAlive On
MaxRequestWorkers 50
KeepAliveTimeout 2

sudo systemctl restart apache2

Nginx

sudo nano /etc/nginx/nginx.conf

Set:

worker_processes auto;
worker_connections 1024;

sudo systemctl restart nginx

Solution 4: Tune the database

Turn on the slow query log, so you can find heavy queries:

sudo nano /etc/mysql/my.cnf

slow_query_log = 1
long_query_time = 2

Restart MySQL:

sudo systemctl restart mysql

Then read the slow query log and add indexes or fix the slow queries.

Solution 5: Limit Docker containers

In a Compose file, add a CPU limit:

deploy:
  resources:
    limits:
      cpus: '1.0'

Or on the command line: docker run --cpus="1.0" image.

More ideas

• Use caching (a page cache, OPcache, Redis).
• Block bad bots and abusive IP addresses.
• Check for malware or a crypto miner if an unknown process uses the CPU.
• Upgrade your plan if the load is real and constant.

Quick recap

• Find the process with top or htop.
• Restart it, tune Apache, Nginx or MySQL, and limit containers.
• Add caching, or add more CPU if you need it.