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name: Tune Runner VM performance
description: tunes the GitHub Runner VM operation system
runs:
  using: composite
  steps:
    - run: |
        if [[ "$OSTYPE" == "linux-gnu"* ]]; then
            # Ensure that reverse lookups for current hostname are handled properly
            # Add the current IP address, long hostname and short hostname record to /etc/hosts file
            echo -e "$(ip addr show eth0 | grep "inet\b" | awk '{print $2}' | cut -d/ -f1)\t$(hostname -f) $(hostname -s)" | sudo tee -a /etc/hosts

            # The default vm.swappiness setting is 60 which has a tendency to start swapping when memory
            # consumption is high.
            # Set vm.swappiness=1 to avoid swapping and allow high RAM usage
            echo 1 | sudo tee /proc/sys/vm/swappiness
            # Set swappiness to 1 for all cgroups and sub-groups
            for swappiness_dir in /sys/fs/cgroup/memory/*/ /sys/fs/cgroup/memory/*/*/; do
              if [ -d "swappiness_dir" ]; then
                echo 1 | sudo tee $(swappiness_dir)memory.swappiness > /dev/null
              fi
            done

            # use "madvise" Linux Transparent HugePages (THP) setting
            # https://www.kernel.org/doc/html/latest/admin-guide/mm/transhuge.html
            # "madvise" is generally a better option than the default "always" setting
            echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/enabled

            # tune filesystem mount options, https://www.kernel.org/doc/Documentation/filesystems/ext4.txt
            # commit=999999, effectively disables automatic syncing to disk (default is every 5 seconds)
            # nobarrier/barrier=0, loosen data consistency on system crash (no negative impact to empheral CI nodes)
            sudo mount -o remount,nodiscard,commit=999999,barrier=0 /
            sudo mount -o remount,nodiscard,commit=999999,barrier=0 /mnt
            # disable discard/trim at device level since remount with nodiscard doesn't seem to be effective
            # https://www.spinics.net/lists/linux-ide/msg52562.html
            for i in /sys/block/sd*/queue/discard_max_bytes; do
              echo 0 | sudo tee $i
            done
            # disable any background jobs that run SSD discard/trim
            sudo systemctl disable fstrim.timer || true
            sudo systemctl stop fstrim.timer || true
            sudo systemctl disable fstrim.service || true
            sudo systemctl stop fstrim.service || true

            # stop php-fpm
            sudo systemctl stop php8.0-fpm.service || true
            sudo systemctl stop php7.4-fpm.service || true
            # stop mono-xsp4
            sudo systemctl disable mono-xsp4.service || true
            sudo systemctl stop mono-xsp4.service || true
            sudo killall mono || true

            # stop Azure Linux agent to save RAM
            sudo systemctl stop walinuxagent.service || true

            # show memory
            free -m
            # show disk
            df -h
            # show cggroup
            echo "/actions_job cgroup settings:"
            sudo cgget actions_job
        fi
      shell: bash