遇到 out of memory 後幾個設定減少的方式

# swap memory (not real memory) 調整到 8g
dd if=/dev/zero of=/backup/swapfile.img bs=8192 count=1048576
mkswap -f /backup/swapfile.img
chmod 0600 /backup/swapfile.img
swapon /backup/swapfile.img

# /etc/fstab 加入
echo '/backup/swapfile.img   swap        swap    defaults    0 0' >> /etc/fstab

# MaxRequestsPerChild  從 4000 調為 2000 減少子程序佔用

# 讓 out of memory 機率降低
sysctl -w vm.panic_on_oom=1      # out of memory，預設 0
sysctl -w vm.overcommit_memory=1 # out of memory，預設 0
sysctl -w vm.overcommit_ratio=0  # out of memory，預設 50

# 降低連線程序佔用
sysctl -w net.ipv4.tcp_syncookies=1   # time wait，防止 syn flood，預設 1
sysctl -w net.ipv4.tcp_tw_reuse=1     # time wait，允許將 time-wait sockets重新用於新的tcp連線上，預設 0
sysctl -w net.ipv4.tcp_tw_recycle=1   # time wait，允許快速回收，預設為0
sysctl -w net.ipv4.tcp_fin_timeout=30 # time wait，timeout 時間，預設 60