arc/setup/etc/arc-ureadahead-trace.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 in trace mode for ARC++"
author        "chromium-os-dev@chromium.org"

# NOTE: this job is not automatically started on boot-up as it is
#       expected to be started manually as needed e.g. when the
#       android container is started without the pack file for the
#       container. This job should not run while arc-ureadahead.conf
#       is running. The existence of the pack and the user's opt-in
#       status of ARC++ decide if the job runs or not.

stop on arc-booted or stop-arc-instance or stopping ui

# Give ureadahead extra time after SIGTERM to write out the pack file.
kill timeout 30

env LOGFILE=/var/log/arc-ureadahead-trace.log
env ROOT=/opt/google/containers/android/rootfs/root

script
  {
    echo "Start arc-ureadahead-trace"
    set -x

    # This is a temporary workaround to make ureadahead in tracing mode
    # work with squashfs. The kernel always reports that loopN device is
    # backed by a rotational device (HDD) which is not true, and that
    # confuses ureadahead.
    # TODO(yusukes): Revert this change once the kernel side fix is landed
    # (https://chromium-review.googlesource.com/#/c/342531/) to all kernel
    # versions we use. Once the patch is landed, queue/rotational will be
    # 0 from the beginning.
    LOOP_MINOR=$(stat --printf='%D' $ROOT | tail -c 1)
    echo 0 > /sys/block/loop$LOOP_MINOR/queue/rotational

    exec ureadahead --quiet --force-trace --path-prefix=$ROOT $ROOT
  } 2>&1 | logger -t "${UPSTART_JOB}"
end script

post-stop exec logger -t "${UPSTART_JOB}" "Post-stop arc-ureadahead-trace"