arc/setup/etc/arc-ureadahead.conf

# Copyright 2016 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

description   "Run ureadahead for ARC++"
author        "chromium-os-dev@chromium.org"

# Run this job in parallel with arc_setup_wrapper.sh run_oci hook. The job
# shouldn't be started until 'ureadahead' (which may be in tracing mode)
# is stopped, otherwise ureadahead may corrupt the $PACK file. Depending
# on start-arc-instance ensures that.
start on start-arc-instance

script
  PACK=/var/lib/ureadahead/opt.google.containers.android.rootfs.root.pack

  {
    ANDROID_ROOTFS_DIR=/opt/google/containers/android/rootfs/root
    SYSTEM_IMAGE=/opt/google/containers/android/system.raw.img

    echo "Start arc-ureadahead"
    set -x

    # Read-ahead files in the image.
    if [ -f "${PACK}" ] && [ ! -L "${PACK}" ]; then
      # The pack file size is usually 90-100KB. Remove the file if the size is
      # <= 60KB.
      MINSIZE=60k
      FILE=$(find "${PACK}" -newer "${SYSTEM_IMAGE}" -size +"${MINSIZE}")
      if [ -n "${FILE}" ]; then
        # Run ureadahead. If it fails, probably because the pack file is too old
        # (>30 days) or is corrupted, remove it.
        # Note: when ureadahead is executed with a mount point argument, it does
        # not automatically switch into tracing mode even when the pack file is
        # not valid.
        ureadahead "${ANDROID_ROOTFS_DIR}" || rm -f "${PACK}"
      else
        # Remove the pack file if it exists but is older than the image.
        rm -f "${PACK}"
      fi
    else
      # In case it's a weird path, nuke it.
      rm -rf "${PACK}"
    fi
  } 2>&1 | logger -t "${UPSTART_JOB}"

  # The pack file is not available or corrupted. Fall back to arc-setup's
  # read-ahead to minimize the performance impact.
  if [ ! -e "${PACK}" ]; then
    exec /usr/sbin/arc-setup --mode=read-ahead "--log_tag=${UPSTART_JOB}"
  fi
end script