High CPU Usage and Solutions in Linux

High CPU usage is one of the most common issues that directly affect server performance. Excessive CPU load can slow down the server, delay application responses, or even cause system crashes. In this article, we’ll cover the main causes of high CPU usage and how to fix them.

Causes of High CPU Usage

1. Resource-Intensive Applications:
   • Web servers (e.g., Apache, Nginx) under heavy load can increase CPU usage significantly.
   • Complex or unoptimized database queries can consume large amounts of CPU.
2. Misconfigured Services:
   • Improperly configured cron jobs or background services.
   • Unnecessary applications or processes running in the background.
3. Malware and Cyber Attacks:
   • DDoS attacks or malicious software can exhaust CPU resources.
   • Crypto-mining malware (cryptojacking).
4. Insufficient RAM:
   • When RAM is full, the system uses swap space, which increases CPU load.
5. Heavy Logging and Disk I/O:
   • Applications that frequently read/write large files can spike CPU usage.

How to Diagnose High CPU Usage

1. Analyze CPU Usage

• Use top or htop to view active processes and their CPU usage.
• Run ps aux --sort=-%cpu | head -10 to list the top CPU-consuming processes.

2. Check Running Services

• Use systemctl list-units --type=service to list active services.
• Stop unnecessary services using systemctl stop [service-name].

3. Scan for DDoS or Malware

• Run netstat -antp to inspect open and suspicious connections.
• Use tools like clamscan or rkhunter to scan for malware.

How to Prevent and Fix High CPU Usage

1. Terminate Unnecessary Processes

• Use kill -9 [PID] to stop processes consuming too much CPU.
• Prevent unwanted services from starting on boot using systemctl disable [service-name].

2. Optimize Server Load

• Adjust worker settings in Apache or Nginx for optimal performance.
• Tune PHP-FPM or MySQL configurations according to your server capacity.

3. Strengthen Security Measures

• Use security tools like Fail2Ban or CSF to block attack attempts.
• Set up firewalls (iptables or ufw) to restrict unwanted access.

4. Manage Resources Efficiently

• Configure swap space properly to reduce pressure on CPU.
• Use nice and renice to prioritize essential processes.