How to Check and Reduce High Memory (RAM) Usage on Linux

High memory usage can cause slow performance, service crashes, and unexpected out-of-memory errors on a Linux VPS.

Step 1: Check Current Memory Usage

Start by viewing overall RAM usage.

free -h

Focus on used, available, and swap memory.

Step 2: Monitor Memory Usage in Real Time

Use top to identify processes consuming the most memory.

top

Press M to sort by memory usage.

Step 3: Use htop for Better Visibility

htop makes memory analysis easier.

sudo apt update
sudo apt install htop -y
htop

Memory usage is shown per process in real time.

Step 4: Identify Memory-Hungry Processes

Once you identify the PID, inspect it further.

ps -fp PID

Replace PID with the process ID.

Step 5: Restart or Stop the Problematic Service

Restarting often frees leaked memory.

sudo systemctl restart service_name

Or stop the process if it is unnecessary.

sudo kill PID

Step 6: Clear Page Cache and Buffers

Linux uses free RAM for caching. Clearing cache may temporarily free memory.

sudo sync
sudo echo 3 > /proc/sys/vm/drop_caches

Use this only for troubleshooting.

Step 7: Check Swap Usage

Heavy swap usage indicates RAM pressure.

swapon --show

If swap is constantly used, consider increasing RAM or optimizing services.

Step 8: Limit Memory Usage for Processes

Prevent a single service from consuming all memory.

sudo systemctl set-property service_name MemoryMax=512M

This limits the service to 512MB RAM.

You may also want to review this related article: Fix High CPU Usage on a Linux VPS

Optional Step: Enable OOM Protection

Ensure the system kills misbehaving processes before crashing.

sudo sysctl vm.overcommit_memory=2