Fix High RAM Usage

Understanding Linux Memory

Linux uses available RAM for caching. "Used" memory isn't always bad. Check:

free -h
free -h -w  # Shows cache separately

Output example:

              total        used        free      shared  buff/cache   available
Mem:           3.9G        1.2G        200M         50M        2.5G        2.4G

Available is the real free memory. If cache is high but available is low, you have a problem.

Find Memory-Hungry Processes

ps aux --sort=-%mem | head -10

sudo apt install smem -y
sudo smem -r -k -t

Common High RAM Culprits

1. MySQL/MariaDB

mysql -e "SHOW VARIABLES LIKE 'innodb_buffer_pool_size';"

Reduce to 60-70% of total RAM:

sudo nano /etc/mysql/my.cnf
# innodb_buffer_pool_size = 1G (for 2GB VPS)

2. PHP-FPM

ps --no-headers -o "rss,cmd" -C php-fpm | awk '{ sum+=$1 } END { printf "%d%s
", sum/NR/1024, "MB" }'

sudo nano /etc/php/*/fpm/pool.d/www.conf
# pm.max_children = (Total RAM - 1GB) / Process Memory per child

3. Apache (Prefork MPM)

sudo a2dismod mpm_prefork
sudo a2enmod mpm_event
sudo systemctl restart apache2

4. Node.js Applications

node --max-old-space-size=512 app.js

5. Memory Leaks

watch -n 5 "ps aux --sort=-%mem | head -5"
sudo systemctl restart leaky-service

Free Up Memory Without Reboot

sudo sync && echo 1 > /proc/sys/vm/drop_caches
sudo sync && echo 2 > /proc/sys/vm/drop_caches
sudo sync && echo 3 > /proc/sys/vm/drop_caches
echo f > /proc/sysrq-trigger