Configure Linux memory management and swap optimization for high-performance workloads

#!/usr/bin/env bash
set -euo pipefail

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m'

# Global variables
SWAP_SIZE=${1:-4G}
TOTAL_STEPS=7

print_status() {
    echo -e "${BLUE}[INFO]${NC} $1"
}

print_success() {
    echo -e "${GREEN}[SUCCESS]${NC} $1"
}

print_warning() {
    echo -e "${YELLOW}[WARNING]${NC} $1"
}

print_error() {
    echo -e "${RED}[ERROR]${NC} $1"
}

usage() {
    echo "Usage: $0 [SWAP_SIZE]"
    echo "  SWAP_SIZE: Size of swap file (default: 4G)"
    echo "  Examples: $0 8G, $0 2G"
    exit 1
}

cleanup() {
    print_error "Script failed. Cleaning up..."
    if [ -f /swapfile.new ]; then
        sudo swapoff /swapfile.new 2>/dev/null || true
        sudo rm -f /swapfile.new
    fi
    if [ -f /etc/sysctl.d/99-memory-optimization.conf.new ]; then
        sudo rm -f /etc/sysctl.d/99-memory-optimization.conf.new
    fi
    exit 1
}

trap cleanup ERR

check_prerequisites() {
    if [[ $EUID -ne 0 ]] && ! sudo -n true 2>/dev/null; then
        print_error "This script requires root privileges or passwordless sudo"
        exit 1
    fi

    if [[ "$SWAP_SIZE" =~ ^[0-9]+[GMK]?$ ]]; then
        :
    else
        print_error "Invalid swap size format. Use format like 4G, 8G, 2048M"
        usage
    fi
}

detect_distro() {
    if [ -f /etc/os-release ]; then
        . /etc/os-release
        case "$ID" in
            ubuntu|debian)
                PKG_MGR="apt"
                PKG_INSTALL="apt install -y"
                PKG_UPDATE="apt update"
                PROCPS_PKG="procps"
                ;;
            almalinux|rocky|centos|rhel|ol|fedora)
                PKG_MGR="dnf"
                PKG_INSTALL="dnf install -y"
                PKG_UPDATE="dnf update -y"
                PROCPS_PKG="procps-ng"
                ;;
            amzn)
                PKG_MGR="yum"
                PKG_INSTALL="yum install -y"
                PKG_UPDATE="yum update -y"
                PROCPS_PKG="procps-ng"
                ;;
            *)
                print_error "Unsupported distribution: $ID"
                exit 1
                ;;
        esac
    else
        print_error "Cannot detect distribution"
        exit 1
    fi
    print_success "Detected distribution: $PRETTY_NAME"
}

install_monitoring_tools() {
    echo "[1/$TOTAL_STEPS] Installing memory monitoring tools..."
    
    print_status "Updating package repositories..."
    sudo $PKG_UPDATE > /dev/null 2>&1
    
    print_status "Installing monitoring tools..."
    sudo $PKG_INSTALL htop iotop sysstat $PROCPS_PKG util-linux > /dev/null 2>&1
    
    print_success "Memory monitoring tools installed"
}

analyze_current_memory() {
    echo "[2/$TOTAL_STEPS] Analyzing current memory configuration..."
    
    print_status "Current memory status:"
    free -h
    echo
    
    print_status "Current swap configuration:"
    swapon --show 2>/dev/null || echo "No swap currently active"
    
    print_success "Memory analysis complete"
}

configure_swap() {
    echo "[3/$TOTAL_STEPS] Configuring optimized swap file..."
    
    # Backup fstab
    sudo cp /etc/fstab /etc/fstab.backup.$(date +%Y%m%d_%H%M%S)
    
    # Disable existing swap
    if swapon --show | grep -q "/swapfile"; then
        print_status "Disabling existing swap..."
        sudo swapoff /swapfile 2>/dev/null || true
    fi
    
    # Remove old swap entries from fstab
    sudo sed -i.bak '/\/swapfile.*swap/d' /etc/fstab
    
    # Create new swap file
    print_status "Creating ${SWAP_SIZE} swap file..."
    sudo fallocate -l "$SWAP_SIZE" /swapfile.new
    sudo chmod 600 /swapfile.new
    sudo mkswap /swapfile.new > /dev/null 2>&1
    
    # Replace old swap file
    if [ -f /swapfile ]; then
        sudo rm /swapfile
    fi
    sudo mv /swapfile.new /swapfile
    
    # Enable swap
    sudo swapon /swapfile
    
    # Add to fstab
    echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab > /dev/null
    
    print_success "Swap file configured successfully"
}

configure_memory_parameters() {
    echo "[4/$TOTAL_STEPS] Configuring memory management parameters..."
    
    # Create sysctl configuration
    sudo tee /etc/sysctl.d/99-memory-optimization.conf.new > /dev/null << 'EOF'
# Memory Management Optimization for High-Performance Workloads
# Swap behavior optimization
vm.swappiness=10
vm.vfs_cache_pressure=50

# Memory overcommit strategy (strict accounting)
vm.overcommit_memory=2
vm.overcommit_ratio=80

# Dirty page handling for better I/O performance
vm.dirty_ratio=15
vm.dirty_background_ratio=5
vm.dirty_expire_centisecs=3000
vm.dirty_writeback_centisecs=500

# Memory reclaim optimization
vm.min_free_kbytes=65536
vm.zone_reclaim_mode=0

# OOM killer tuning
vm.panic_on_oom=0
vm.oom_kill_allocating_task=1

# Shared memory optimization
kernel.shmmax=68719476736
kernel.shmall=4294967296
EOF

    sudo mv /etc/sysctl.d/99-memory-optimization.conf.new /etc/sysctl.d/99-memory-optimization.conf
    sudo chmod 644 /etc/sysctl.d/99-memory-optimization.conf
    
    # Apply settings
    sudo sysctl -p /etc/sysctl.d/99-memory-optimization.conf > /dev/null 2>&1
    
    print_success "Memory management parameters configured"
}

configure_transparent_hugepages() {
    echo "[5/$TOTAL_STEPS] Configuring Transparent Huge Pages..."
    
    # Create systemd service to disable THP
    sudo tee /etc/systemd/system/disable-thp.service > /dev/null << 'EOF'
[Unit]
Description=Disable Transparent Huge Pages (THP)
DefaultDependencies=no
After=sysinit.target local-fs.target
Before=mongod.service mysqld.service postgresql.service

[Service]
Type=oneshot
ExecStart=/bin/sh -c 'echo never | tee /sys/kernel/mm/transparent_hugepage/enabled > /dev/null'
ExecStart=/bin/sh -c 'echo never | tee /sys/kernel/mm/transparent_hugepage/defrag > /dev/null'
RemainAfterExit=true

[Install]
WantedBy=multi-user.target
EOF

    sudo chmod 644 /etc/systemd/system/disable-thp.service
    sudo systemctl daemon-reload
    sudo systemctl enable disable-thp.service > /dev/null 2>&1
    sudo systemctl start disable-thp.service > /dev/null 2>&1
    
    print_success "Transparent Huge Pages disabled"
}

configure_zram() {
    echo "[6/$TOTAL_STEPS] Installing and configuring zram..."
    
    # Install zram-tools based on distro
    if [[ "$PKG_MGR" == "apt" ]]; then
        sudo $PKG_INSTALL zram-tools > /dev/null 2>&1
        
        # Configure zram
        sudo tee /etc/default/zramswap > /dev/null << 'EOF'
ALGO=lz4
PERCENT=25
SIZE=1024M
EOF
        sudo systemctl enable zramswap > /dev/null 2>&1
        sudo systemctl start zramswap > /dev/null 2>&1
    else
        # For RHEL-based systems, use zram-generator
        sudo $PKG_INSTALL zram-generator > /dev/null 2>&1
        
        sudo mkdir -p /etc/systemd/zram-generator.conf.d
        sudo tee /etc/systemd/zram-generator.conf.d/zram-swap.conf > /dev/null << 'EOF'
[zram0]
zram-size = min(ram / 4, 2048)
compression-algorithm = lz4
EOF
        sudo systemctl daemon-reload
        sudo systemctl enable --now systemd-zram-setup@zram0.service > /dev/null 2>&1
    fi
    
    print_success "zram configured for memory compression"
}

verify_configuration() {
    echo "[7/$TOTAL_STEPS] Verifying configuration..."
    
    print_status "Checking swap configuration:"
    swapon --show
    echo
    
    print_status "Checking memory parameters:"
    sysctl vm.swappiness vm.vfs_cache_pressure vm.overcommit_memory
    echo
    
    print_status "Checking Transparent Huge Pages:"
    cat /sys/kernel/mm/transparent_hugepage/enabled
    echo
    
    print_status "Checking zram:"
    if command -v zramctl > /dev/null; then
        zramctl 2>/dev/null || echo "zram devices not yet initialized"
    fi
    
    print_success "Configuration verification complete"
}

main() {
    echo "Linux Memory Management Optimization Script"
    echo "==========================================="
    echo
    
    check_prerequisites
    detect_distro
    install_monitoring_tools
    analyze_current_memory
    configure_swap
    configure_memory_parameters
    configure_transparent_hugepages
    configure_zram
    verify_configuration
    
    echo
    print_success "Memory optimization completed successfully!"
    print_warning "Some changes require a reboot to take full effect"
    print_status "Monitor your system performance and adjust parameters as needed"
}

main "$@"