Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 781 insertions, 0 deletions

diff --git a/Documentation/admin-guide/laptops/laptop-mode.rst b/Documentation/admin-guide/laptops/laptop-mode.rst
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+===============================================
+How to conserve battery power using laptop-mode
+===============================================
+
+Document Author: Bart Samwel (bart@samwel.tk)
+
+Date created: January 2, 2004
+
+Last modified: December 06, 2004
+
+Introduction
+------------
+
+Laptop mode is used to minimize the time that the hard disk needs to be spun up,
+to conserve battery power on laptops. It has been reported to cause significant
+power savings.
+
+.. Contents
+
+   * Introduction
+   * Installation
+   * Caveats
+   * The Details
+   * Tips & Tricks
+   * Control script
+   * ACPI integration
+   * Monitoring tool
+
+
+Installation
+------------
+
+To use laptop mode, you don't need to set any kernel configuration options
+or anything. Simply install all the files included in this document, and
+laptop mode will automatically be started when you're on battery. For
+your convenience, a tarball containing an installer can be downloaded at:
+
+	http://www.samwel.tk/laptop_mode/laptop_mode/
+
+To configure laptop mode, you need to edit the configuration file, which is
+located in /etc/default/laptop-mode on Debian-based systems, or in
+/etc/sysconfig/laptop-mode on other systems.
+
+Unfortunately, automatic enabling of laptop mode does not work for
+laptops that don't have ACPI. On those laptops, you need to start laptop
+mode manually. To start laptop mode, run "laptop_mode start", and to
+stop it, run "laptop_mode stop". (Note: The laptop mode tools package now
+has experimental support for APM, you might want to try that first.)
+
+
+Caveats
+-------
+
+* The downside of laptop mode is that you have a chance of losing up to 10
+  minutes of work. If you cannot afford this, don't use it! The supplied ACPI
+  scripts automatically turn off laptop mode when the battery almost runs out,
+  so that you won't lose any data at the end of your battery life.
+
+* Most desktop hard drives have a very limited lifetime measured in spindown
+  cycles, typically about 50.000 times (it's usually listed on the spec sheet).
+  Check your drive's rating, and don't wear down your drive's lifetime if you
+  don't need to.
+
+* If you mount some of your ext3/reiserfs filesystems with the -n option, then
+  the control script will not be able to remount them correctly. You must set
+  DO_REMOUNTS=0 in the control script, otherwise it will remount them with the
+  wrong options -- or it will fail because it cannot write to /etc/mtab.
+
+* If you have your filesystems listed as type "auto" in fstab, like I did, then
+  the control script will not recognize them as filesystems that need remounting.
+  You must list the filesystems with their true type instead.
+
+* It has been reported that some versions of the mutt mail client use file access
+  times to determine whether a folder contains new mail. If you use mutt and
+  experience this, you must disable the noatime remounting by setting the option
+  DO_REMOUNT_NOATIME to 0 in the configuration file.
+
+
+The Details
+-----------
+
+Laptop mode is controlled by the knob /proc/sys/vm/laptop_mode. This knob is
+present for all kernels that have the laptop mode patch, regardless of any
+configuration options. When the knob is set, any physical disk I/O (that might
+have caused the hard disk to spin up) causes Linux to flush all dirty blocks. The
+result of this is that after a disk has spun down, it will not be spun up
+anymore to write dirty blocks, because those blocks had already been written
+immediately after the most recent read operation. The value of the laptop_mode
+knob determines the time between the occurrence of disk I/O and when the flush
+is triggered. A sensible value for the knob is 5 seconds. Setting the knob to
+0 disables laptop mode.
+
+To increase the effectiveness of the laptop_mode strategy, the laptop_mode
+control script increases dirty_expire_centisecs and dirty_writeback_centisecs in
+/proc/sys/vm to about 10 minutes (by default), which means that pages that are
+dirtied are not forced to be written to disk as often. The control script also
+changes the dirty background ratio, so that background writeback of dirty pages
+is not done anymore. Combined with a higher commit value (also 10 minutes) for
+ext3 or ReiserFS filesystems (also done automatically by the control script),
+this results in concentration of disk activity in a small time interval which
+occurs only once every 10 minutes, or whenever the disk is forced to spin up by
+a cache miss. The disk can then be spun down in the periods of inactivity.
+
+If you want to find out which process caused the disk to spin up, you can
+gather information by setting the flag /proc/sys/vm/block_dump. When this flag
+is set, Linux reports all disk read and write operations that take place, and
+all block dirtyings done to files. This makes it possible to debug why a disk
+needs to spin up, and to increase battery life even more. The output of
+block_dump is written to the kernel output, and it can be retrieved using
+"dmesg". When you use block_dump and your kernel logging level also includes
+kernel debugging messages, you probably want to turn off klogd, otherwise
+the output of block_dump will be logged, causing disk activity that is not
+normally there.
+
+
+Configuration
+-------------
+
+The laptop mode configuration file is located in /etc/default/laptop-mode on
+Debian-based systems, or in /etc/sysconfig/laptop-mode on other systems. It
+contains the following options:
+
+MAX_AGE:
+
+Maximum time, in seconds, of hard drive spindown time that you are
+comfortable with. Worst case, it's possible that you could lose this
+amount of work if your battery fails while you're in laptop mode.
+
+MINIMUM_BATTERY_MINUTES:
+
+Automatically disable laptop mode if the remaining number of minutes of
+battery power is less than this value. Default is 10 minutes.
+
+AC_HD/BATT_HD:
+
+The idle timeout that should be set on your hard drive when laptop mode
+is active (BATT_HD) and when it is not active (AC_HD). The defaults are
+20 seconds (value 4) for BATT_HD  and 2 hours (value 244) for AC_HD. The
+possible values are those listed in the manual page for "hdparm" for the
+"-S" option.
+
+HD:
+
+The devices for which the spindown timeout should be adjusted by laptop mode.
+Default is /dev/hda. If you specify multiple devices, separate them by a space.
+
+READAHEAD:
+
+Disk readahead, in 512-byte sectors, while laptop mode is active. A large
+readahead can prevent disk accesses for things like executable pages (which are
+loaded on demand while the application executes) and sequentially accessed data
+(MP3s).
+
+DO_REMOUNTS:
+
+The control script automatically remounts any mounted journaled filesystems
+with appropriate commit interval options. When this option is set to 0, this
+feature is disabled.
+
+DO_REMOUNT_NOATIME:
+
+When remounting, should the filesystems be remounted with the noatime option?
+Normally, this is set to "1" (enabled), but there may be programs that require
+access time recording.
+
+DIRTY_RATIO:
+
+The percentage of memory that is allowed to contain "dirty" or unsaved data
+before a writeback is forced, while laptop mode is active. Corresponds to
+the /proc/sys/vm/dirty_ratio sysctl.
+
+DIRTY_BACKGROUND_RATIO:
+
+The percentage of memory that is allowed to contain "dirty" or unsaved data
+after a forced writeback is done due to an exceeding of DIRTY_RATIO. Set
+this nice and low. This corresponds to the /proc/sys/vm/dirty_background_ratio
+sysctl.
+
+Note that the behaviour of dirty_background_ratio is quite different
+when laptop mode is active and when it isn't. When laptop mode is inactive,
+dirty_background_ratio is the threshold percentage at which background writeouts
+start taking place. When laptop mode is active, however, background writeouts
+are disabled, and the dirty_background_ratio only determines how much writeback
+is done when dirty_ratio is reached.
+
+DO_CPU:
+
+Enable CPU frequency scaling when in laptop mode. (Requires CPUFreq to be setup.
+See Documentation/admin-guide/pm/cpufreq.rst for more info. Disabled by default.)
+
+CPU_MAXFREQ:
+
+When on battery, what is the maximum CPU speed that the system should use? Legal
+values are "slowest" for the slowest speed that your CPU is able to operate at,
+or a value listed in /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies.
+
+
+Tips & Tricks
+-------------
+
+* Bartek Kania reports getting up to 50 minutes of extra battery life (on top
+  of his regular 3 to 3.5 hours) using a spindown time of 5 seconds (BATT_HD=1).
+
+* You can spin down the disk while playing MP3, by setting disk readahead
+  to 8MB (READAHEAD=16384). Effectively, the disk will read a complete MP3 at
+  once, and will then spin down while the MP3 is playing. (Thanks to Bartek
+  Kania.)
+
+* Drew Scott Daniels observed: "I don't know why, but when I decrease the number
+  of colours that my display uses it consumes less battery power. I've seen
+  this on powerbooks too. I hope that this is a piece of information that
+  might be useful to the Laptop Mode patch or its users."
+
+* In syslog.conf, you can prefix entries with a dash `-` to omit syncing the
+  file after every logging. When you're using laptop-mode and your disk doesn't
+  spin down, this is a likely culprit.
+
+* Richard Atterer observed that laptop mode does not work well with noflushd
+  (http://noflushd.sourceforge.net/), it seems that noflushd prevents laptop-mode
+  from doing its thing.
+
+* If you're worried about your data, you might want to consider using a USB
+  memory stick or something like that as a "working area". (Be aware though
+  that flash memory can only handle a limited number of writes, and overuse
+  may wear out your memory stick pretty quickly. Do _not_ use journalling
+  filesystems on flash memory sticks.)
+
+
+Configuration file for control and ACPI battery scripts
+-------------------------------------------------------
+
+This allows the tunables to be changed for the scripts via an external
+configuration file
+
+It should be installed as /etc/default/laptop-mode on Debian, and as
+/etc/sysconfig/laptop-mode on Red Hat, SUSE, Mandrake, and other work-alikes.
+
+Config file::
+
+  # Maximum time, in seconds, of hard drive spindown time that you are
+  # comfortable with. Worst case, it's possible that you could lose this
+  # amount of work if your battery fails you while in laptop mode.
+  #MAX_AGE=600
+
+  # Automatically disable laptop mode when the number of minutes of battery
+  # that you have left goes below this threshold.
+  MINIMUM_BATTERY_MINUTES=10
+
+  # Read-ahead, in 512-byte sectors. You can spin down the disk while playing MP3/OGG
+  # by setting the disk readahead to 8MB (READAHEAD=16384). Effectively, the disk
+  # will read a complete MP3 at once, and will then spin down while the MP3/OGG is
+  # playing.
+  #READAHEAD=4096
+
+  # Shall we remount journaled fs. with appropriate commit interval? (1=yes)
+  #DO_REMOUNTS=1
+
+  # And shall we add the "noatime" option to that as well? (1=yes)
+  #DO_REMOUNT_NOATIME=1
+
+  # Dirty synchronous ratio.  At this percentage of dirty pages the process
+  # which
+  # calls write() does its own writeback
+  #DIRTY_RATIO=40
+
+  #
+  # Allowed dirty background ratio, in percent.  Once DIRTY_RATIO has been
+  # exceeded, the kernel will wake flusher threads which will then reduce the
+  # amount of dirty memory to dirty_background_ratio.  Set this nice and low,
+  # so once some writeout has commenced, we do a lot of it.
+  #
+  #DIRTY_BACKGROUND_RATIO=5
+
+  # kernel default dirty buffer age
+  #DEF_AGE=30
+  #DEF_UPDATE=5
+  #DEF_DIRTY_BACKGROUND_RATIO=10
+  #DEF_DIRTY_RATIO=40
+  #DEF_XFS_AGE_BUFFER=15
+  #DEF_XFS_SYNC_INTERVAL=30
+  #DEF_XFS_BUFD_INTERVAL=1
+
+  # This must be adjusted manually to the value of HZ in the running kernel
+  # on 2.4, until the XFS people change their 2.4 external interfaces to work in
+  # centisecs. This can be automated, but it's a work in progress that still
+  # needs# some fixes. On 2.6 kernels, XFS uses USER_HZ instead of HZ for
+  # external interfaces, and that is currently always set to 100. So you don't
+  # need to change this on 2.6.
+  #XFS_HZ=100
+
+  # Should the maximum CPU frequency be adjusted down while on battery?
+  # Requires CPUFreq to be setup.
+  # See Documentation/admin-guide/pm/cpufreq.rst for more info
+  #DO_CPU=0
+
+  # When on battery what is the maximum CPU speed that the system should
+  # use? Legal values are "slowest" for the slowest speed that your
+  # CPU is able to operate at, or a value listed in:
+  # /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
+  # Only applicable if DO_CPU=1.
+  #CPU_MAXFREQ=slowest
+
+  # Idle timeout for your hard drive (man hdparm for valid values, -S option)
+  # Default is 2 hours on AC (AC_HD=244) and 20 seconds for battery (BATT_HD=4).
+  #AC_HD=244
+  #BATT_HD=4
+
+  # The drives for which to adjust the idle timeout. Separate them by a space,
+  # e.g. HD="/dev/hda /dev/hdb".
+  #HD="/dev/hda"
+
+  # Set the spindown timeout on a hard drive?
+  #DO_HD=1
+
+
+Control script
+--------------
+
+Please note that this control script works for the Linux 2.4 and 2.6 series (thanks
+to Kiko Piris).
+
+Control script::
+
+  #!/bin/bash
+
+  # start or stop laptop_mode, best run by a power management daemon when
+  # ac gets connected/disconnected from a laptop
+  #
+  # install as /sbin/laptop_mode
+  #
+  # Contributors to this script:   Kiko Piris
+  #				 Bart Samwel
+  #				 Micha Feigin
+  #				 Andrew Morton
+  #				 Herve Eychenne
+  #				 Dax Kelson
+  #
+  # Original Linux 2.4 version by: Jens Axboe
+
+  #############################################################################
+
+  # Source config
+  if [ -f /etc/default/laptop-mode ] ; then
+	# Debian
+	. /etc/default/laptop-mode
+  elif [ -f /etc/sysconfig/laptop-mode ] ; then
+	# Others
+          . /etc/sysconfig/laptop-mode
+  fi
+
+  # Don't raise an error if the config file is incomplete
+  # set defaults instead:
+
+  # Maximum time, in seconds, of hard drive spindown time that you are
+  # comfortable with. Worst case, it's possible that you could lose this
+  # amount of work if your battery fails you while in laptop mode.
+  MAX_AGE=${MAX_AGE:-'600'}
+
+  # Read-ahead, in kilobytes
+  READAHEAD=${READAHEAD:-'4096'}
+
+  # Shall we remount journaled fs. with appropriate commit interval? (1=yes)
+  DO_REMOUNTS=${DO_REMOUNTS:-'1'}
+
+  # And shall we add the "noatime" option to that as well? (1=yes)
+  DO_REMOUNT_NOATIME=${DO_REMOUNT_NOATIME:-'1'}
+
+  # Shall we adjust the idle timeout on a hard drive?
+  DO_HD=${DO_HD:-'1'}
+
+  # Adjust idle timeout on which hard drive?
+  HD="${HD:-'/dev/hda'}"
+
+  # spindown time for HD (hdparm -S values)
+  AC_HD=${AC_HD:-'244'}
+  BATT_HD=${BATT_HD:-'4'}
+
+  # Dirty synchronous ratio.  At this percentage of dirty pages the process which
+  # calls write() does its own writeback
+  DIRTY_RATIO=${DIRTY_RATIO:-'40'}
+
+  # cpu frequency scaling
+  # See Documentation/admin-guide/pm/cpufreq.rst for more info
+  DO_CPU=${CPU_MANAGE:-'0'}
+  CPU_MAXFREQ=${CPU_MAXFREQ:-'slowest'}
+
+  #
+  # Allowed dirty background ratio, in percent.  Once DIRTY_RATIO has been
+  # exceeded, the kernel will wake flusher threads which will then reduce the
+  # amount of dirty memory to dirty_background_ratio.  Set this nice and low,
+  # so once some writeout has commenced, we do a lot of it.
+  #
+  DIRTY_BACKGROUND_RATIO=${DIRTY_BACKGROUND_RATIO:-'5'}
+
+  # kernel default dirty buffer age
+  DEF_AGE=${DEF_AGE:-'30'}
+  DEF_UPDATE=${DEF_UPDATE:-'5'}
+  DEF_DIRTY_BACKGROUND_RATIO=${DEF_DIRTY_BACKGROUND_RATIO:-'10'}
+  DEF_DIRTY_RATIO=${DEF_DIRTY_RATIO:-'40'}
+  DEF_XFS_AGE_BUFFER=${DEF_XFS_AGE_BUFFER:-'15'}
+  DEF_XFS_SYNC_INTERVAL=${DEF_XFS_SYNC_INTERVAL:-'30'}
+  DEF_XFS_BUFD_INTERVAL=${DEF_XFS_BUFD_INTERVAL:-'1'}
+
+  # This must be adjusted manually to the value of HZ in the running kernel
+  # on 2.4, until the XFS people change their 2.4 external interfaces to work in
+  # centisecs. This can be automated, but it's a work in progress that still needs
+  # some fixes. On 2.6 kernels, XFS uses USER_HZ instead of HZ for external
+  # interfaces, and that is currently always set to 100. So you don't need to
+  # change this on 2.6.
+  XFS_HZ=${XFS_HZ:-'100'}
+
+  #############################################################################
+
+  KLEVEL="$(uname -r |
+               {
+	       IFS='.' read a b c
+	       echo $a.$b
+	     }
+  )"
+  case "$KLEVEL" in
+	"2.4"|"2.6")
+		;;
+	*)
+		echo "Unhandled kernel version: $KLEVEL ('uname -r' = '$(uname -r)')" >&2
+		exit 1
+		;;
+  esac
+
+  if [ ! -e /proc/sys/vm/laptop_mode ] ; then
+	echo "Kernel is not patched with laptop_mode patch." >&2
+	exit 1
+  fi
+
+  if [ ! -w /proc/sys/vm/laptop_mode ] ; then
+	echo "You do not have enough privileges to enable laptop_mode." >&2
+	exit 1
+  fi
+
+  # Remove an option (the first parameter) of the form option=<number> from
+  # a mount options string (the rest of the parameters).
+  parse_mount_opts () {
+	OPT="$1"
+	shift
+	echo ",$*," | sed		\
+	 -e 's/,'"$OPT"'=[0-9]*,/,/g'	\
+	 -e 's/,,*/,/g'			\
+	 -e 's/^,//'			\
+	 -e 's/,$//'
+  }
+
+  # Remove an option (the first parameter) without any arguments from
+  # a mount option string (the rest of the parameters).
+  parse_nonumber_mount_opts () {
+	OPT="$1"
+	shift
+	echo ",$*," | sed		\
+	 -e 's/,'"$OPT"',/,/g'		\
+	 -e 's/,,*/,/g'			\
+	 -e 's/^,//'			\
+	 -e 's/,$//'
+  }
+
+  # Find out the state of a yes/no option (e.g. "atime"/"noatime") in
+  # fstab for a given filesystem, and use this state to replace the
+  # value of the option in another mount options string. The device
+  # is the first argument, the option name the second, and the default
+  # value the third. The remainder is the mount options string.
+  #
+  # Example:
+  # parse_yesno_opts_wfstab /dev/hda1 atime atime defaults,noatime
+  #
+  # If fstab contains, say, "rw" for this filesystem, then the result
+  # will be "defaults,atime".
+  parse_yesno_opts_wfstab () {
+	L_DEV="$1"
+	OPT="$2"
+	DEF_OPT="$3"
+	shift 3
+	L_OPTS="$*"
+	PARSEDOPTS1="$(parse_nonumber_mount_opts $OPT $L_OPTS)"
+	PARSEDOPTS1="$(parse_nonumber_mount_opts no$OPT $PARSEDOPTS1)"
+	# Watch for a default atime in fstab
+	FSTAB_OPTS="$(awk '$1 == "'$L_DEV'" { print $4 }' /etc/fstab)"
+	if echo "$FSTAB_OPTS" | grep "$OPT" > /dev/null ; then
+		# option specified in fstab: extract the value and use it
+		if echo "$FSTAB_OPTS" | grep "no$OPT" > /dev/null ; then
+			echo "$PARSEDOPTS1,no$OPT"
+		else
+			# no$OPT not found -- so we must have $OPT.
+			echo "$PARSEDOPTS1,$OPT"
+		fi
+	else
+		# option not specified in fstab -- choose the default.
+		echo "$PARSEDOPTS1,$DEF_OPT"
+	fi
+  }
+
+  # Find out the state of a numbered option (e.g. "commit=NNN") in
+  # fstab for a given filesystem, and use this state to replace the
+  # value of the option in another mount options string. The device
+  # is the first argument, and the option name the second. The
+  # remainder is the mount options string in which the replacement
+  # must be done.
+  #
+  # Example:
+  # parse_mount_opts_wfstab /dev/hda1 commit defaults,commit=7
+  #
+  # If fstab contains, say, "commit=3,rw" for this filesystem, then the
+  # result will be "rw,commit=3".
+  parse_mount_opts_wfstab () {
+	L_DEV="$1"
+	OPT="$2"
+	shift 2
+	L_OPTS="$*"
+	PARSEDOPTS1="$(parse_mount_opts $OPT $L_OPTS)"
+	# Watch for a default commit in fstab
+	FSTAB_OPTS="$(awk '$1 == "'$L_DEV'" { print $4 }' /etc/fstab)"
+	if echo "$FSTAB_OPTS" | grep "$OPT=" > /dev/null ; then
+		# option specified in fstab: extract the value, and use it
+		echo -n "$PARSEDOPTS1,$OPT="
+		echo ",$FSTAB_OPTS," | sed \
+		 -e 's/.*,'"$OPT"'=//'	\
+		 -e 's/,.*//'
+	else
+		# option not specified in fstab: set it to 0
+		echo "$PARSEDOPTS1,$OPT=0"
+	fi
+  }
+
+  deduce_fstype () {
+	MP="$1"
+	# My root filesystem unfortunately has
+	# type "unknown" in /etc/mtab. If we encounter
+	# "unknown", we try to get the type from fstab.
+	cat /etc/fstab |
+	grep -v '^#' |
+	while read FSTAB_DEV FSTAB_MP FSTAB_FST FSTAB_OPTS FSTAB_DUMP FSTAB_DUMP ; do
+		if [ "$FSTAB_MP" = "$MP" ]; then
+			echo $FSTAB_FST
+			exit 0
+		fi
+	done
+  }
+
+  if [ $DO_REMOUNT_NOATIME -eq 1 ] ; then
+	NOATIME_OPT=",noatime"
+  fi
+
+  case "$1" in
+	start)
+		AGE=$((100*$MAX_AGE))
+		XFS_AGE=$(($XFS_HZ*$MAX_AGE))
+		echo -n "Starting laptop_mode"
+
+		if [ -d /proc/sys/vm/pagebuf ] ; then
+			# (For 2.4 and early 2.6.)
+			# This only needs to be set, not reset -- it is only used when
+			# laptop mode is enabled.
+			echo $XFS_AGE > /proc/sys/vm/pagebuf/lm_flush_age
+			echo $XFS_AGE > /proc/sys/fs/xfs/lm_sync_interval
+		elif [ -f /proc/sys/fs/xfs/lm_age_buffer ] ; then
+			# (A couple of early 2.6 laptop mode patches had these.)
+			# The same goes for these.
+			echo $XFS_AGE > /proc/sys/fs/xfs/lm_age_buffer
+			echo $XFS_AGE > /proc/sys/fs/xfs/lm_sync_interval
+		elif [ -f /proc/sys/fs/xfs/age_buffer ] ; then
+			# (2.6.6)
+			# But not for these -- they are also used in normal
+			# operation.
+			echo $XFS_AGE > /proc/sys/fs/xfs/age_buffer
+			echo $XFS_AGE > /proc/sys/fs/xfs/sync_interval
+		elif [ -f /proc/sys/fs/xfs/age_buffer_centisecs ] ; then
+			# (2.6.7 upwards)
+			# And not for these either. These are in centisecs,
+			# not USER_HZ, so we have to use $AGE, not $XFS_AGE.
+			echo $AGE > /proc/sys/fs/xfs/age_buffer_centisecs
+			echo $AGE > /proc/sys/fs/xfs/xfssyncd_centisecs
+			echo 3000 > /proc/sys/fs/xfs/xfsbufd_centisecs
+		fi
+
+		case "$KLEVEL" in
+			"2.4")
+				echo 1					> /proc/sys/vm/laptop_mode
+				echo "30 500 0 0 $AGE $AGE 60 20 0"	> /proc/sys/vm/bdflush
+				;;
+			"2.6")
+				echo 5					> /proc/sys/vm/laptop_mode
+				echo "$AGE"				> /proc/sys/vm/dirty_writeback_centisecs
+				echo "$AGE"				> /proc/sys/vm/dirty_expire_centisecs
+				echo "$DIRTY_RATIO"			> /proc/sys/vm/dirty_ratio
+				echo "$DIRTY_BACKGROUND_RATIO"		> /proc/sys/vm/dirty_background_ratio
+				;;
+		esac
+		if [ $DO_REMOUNTS -eq 1 ]; then
+			cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do
+				PARSEDOPTS="$(parse_mount_opts "$OPTS")"
+				if [ "$FST" = 'unknown' ]; then
+					FST=$(deduce_fstype $MP)
+				fi
+				case "$FST" in
+					"ext3"|"reiserfs")
+						PARSEDOPTS="$(parse_mount_opts commit "$OPTS")"
+						mount $DEV -t $FST $MP -o remount,$PARSEDOPTS,commit=$MAX_AGE$NOATIME_OPT
+						;;
+					"xfs")
+						mount $DEV -t $FST $MP -o remount,$OPTS$NOATIME_OPT
+						;;
+				esac
+				if [ -b $DEV ] ; then
+					blockdev --setra $(($READAHEAD * 2)) $DEV
+				fi
+			done
+		fi
+		if [ $DO_HD -eq 1 ] ; then
+			for THISHD in $HD ; do
+				/sbin/hdparm -S $BATT_HD $THISHD > /dev/null 2>&1
+				/sbin/hdparm -B 1 $THISHD > /dev/null 2>&1
+			done
+		fi
+		if [ $DO_CPU -eq 1 -a -e /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq ]; then
+			if [ $CPU_MAXFREQ = 'slowest' ]; then
+				CPU_MAXFREQ=`cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq`
+			fi
+			echo $CPU_MAXFREQ > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
+		fi
+		echo "."
+		;;
+	stop)
+		U_AGE=$((100*$DEF_UPDATE))
+		B_AGE=$((100*$DEF_AGE))
+		echo -n "Stopping laptop_mode"
+		echo 0 > /proc/sys/vm/laptop_mode
+		if [ -f /proc/sys/fs/xfs/age_buffer -a ! -f /proc/sys/fs/xfs/lm_age_buffer ] ; then
+			# These need to be restored, if there are no lm_*.
+			echo $(($XFS_HZ*$DEF_XFS_AGE_BUFFER))	 	> /proc/sys/fs/xfs/age_buffer
+			echo $(($XFS_HZ*$DEF_XFS_SYNC_INTERVAL)) 	> /proc/sys/fs/xfs/sync_interval
+		elif [ -f /proc/sys/fs/xfs/age_buffer_centisecs ] ; then
+			# These need to be restored as well.
+			echo $((100*$DEF_XFS_AGE_BUFFER))	> /proc/sys/fs/xfs/age_buffer_centisecs
+			echo $((100*$DEF_XFS_SYNC_INTERVAL))	> /proc/sys/fs/xfs/xfssyncd_centisecs
+			echo $((100*$DEF_XFS_BUFD_INTERVAL))	> /proc/sys/fs/xfs/xfsbufd_centisecs
+		fi
+		case "$KLEVEL" in
+			"2.4")
+				echo "30 500 0 0 $U_AGE $B_AGE 60 20 0"	> /proc/sys/vm/bdflush
+				;;
+			"2.6")
+				echo "$U_AGE"				> /proc/sys/vm/dirty_writeback_centisecs
+				echo "$B_AGE"				> /proc/sys/vm/dirty_expire_centisecs
+				echo "$DEF_DIRTY_RATIO"			> /proc/sys/vm/dirty_ratio
+				echo "$DEF_DIRTY_BACKGROUND_RATIO"	> /proc/sys/vm/dirty_background_ratio
+				;;
+		esac
+		if [ $DO_REMOUNTS -eq 1 ] ; then
+			cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do
+				# Reset commit and atime options to defaults.
+				if [ "$FST" = 'unknown' ]; then
+					FST=$(deduce_fstype $MP)
+				fi
+				case "$FST" in
+					"ext3"|"reiserfs")
+						PARSEDOPTS="$(parse_mount_opts_wfstab $DEV commit $OPTS)"
+						PARSEDOPTS="$(parse_yesno_opts_wfstab $DEV atime atime $PARSEDOPTS)"
+						mount $DEV -t $FST $MP -o remount,$PARSEDOPTS
+						;;
+					"xfs")
+						PARSEDOPTS="$(parse_yesno_opts_wfstab $DEV atime atime $OPTS)"
+						mount $DEV -t $FST $MP -o remount,$PARSEDOPTS
+						;;
+				esac
+				if [ -b $DEV ] ; then
+					blockdev --setra 256 $DEV
+				fi
+			done
+		fi
+		if [ $DO_HD -eq 1 ] ; then
+			for THISHD in $HD ; do
+				/sbin/hdparm -S $AC_HD $THISHD > /dev/null 2>&1
+				/sbin/hdparm -B 255 $THISHD > /dev/null 2>&1
+			done
+		fi
+		if [ $DO_CPU -eq 1 -a -e /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq ]; then
+			echo `cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq` > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
+		fi
+		echo "."
+		;;
+	*)
+		echo "Usage: $0 {start|stop}" 2>&1
+		exit 1
+		;;
+
+  esac
+
+  exit 0
+
+
+ACPI integration
+----------------
+
+Dax Kelson submitted this so that the ACPI acpid daemon will
+kick off the laptop_mode script and run hdparm. The part that
+automatically disables laptop mode when the battery is low was
+written by Jan Topinski.
+
+/etc/acpi/events/ac_adapter::
+
+	event=ac_adapter
+	action=/etc/acpi/actions/ac.sh %e
+
+/etc/acpi/events/battery::
+
+	event=battery.*
+	action=/etc/acpi/actions/battery.sh %e
+
+/etc/acpi/actions/ac.sh::
+
+  #!/bin/bash
+
+  # ac on/offline event handler
+
+  status=`awk '/^state: / { print $2 }' /proc/acpi/ac_adapter/$2/state`
+
+  case $status in
+          "on-line")
+                  /sbin/laptop_mode stop
+                  exit 0
+          ;;
+          "off-line")
+                  /sbin/laptop_mode start
+                  exit 0
+          ;;
+  esac
+
+
+/etc/acpi/actions/battery.sh::
+
+  #! /bin/bash
+
+  # Automatically disable laptop mode when the battery almost runs out.
+
+  BATT_INFO=/proc/acpi/battery/$2/state
+
+  if [[ -f /proc/sys/vm/laptop_mode ]]
+  then
+     LM=`cat /proc/sys/vm/laptop_mode`
+     if [[ $LM -gt 0 ]]
+     then
+       if [[ -f $BATT_INFO ]]
+       then
+          # Source the config file only now that we know we need
+          if [ -f /etc/default/laptop-mode ] ; then
+                  # Debian
+                  . /etc/default/laptop-mode
+          elif [ -f /etc/sysconfig/laptop-mode ] ; then
+                  # Others
+                  . /etc/sysconfig/laptop-mode
+          fi
+          MINIMUM_BATTERY_MINUTES=${MINIMUM_BATTERY_MINUTES:-'10'}
+
+          ACTION="`cat $BATT_INFO | grep charging | cut -c 26-`"
+          if [[ ACTION -eq "discharging" ]]
+          then
+             PRESENT_RATE=`cat $BATT_INFO | grep "present rate:" | sed  "s/.* \([0-9][0-9]* \).*/\1/" `
+             REMAINING=`cat $BATT_INFO | grep "remaining capacity:" | sed  "s/.* \([0-9][0-9]* \).*/\1/" `
+          fi
+          if (($REMAINING * 60 / $PRESENT_RATE < $MINIMUM_BATTERY_MINUTES))
+          then
+             /sbin/laptop_mode stop
+          fi
+       else
+         logger -p daemon.warning "You are using laptop mode and your battery interface $BATT_INFO is missing. This may lead to loss of data when the battery runs out. Check kernel ACPI support and /proc/acpi/battery folder, and edit /etc/acpi/battery.sh to set BATT_INFO to the correct path."
+       fi
+     fi
+  fi
+
+
+Monitoring tool
+---------------
+
+Bartek Kania submitted this, it can be used to measure how much time your disk
+spends spun up/down.  See tools/laptop/dslm/dslm.c