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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-03-25 03:53:42 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-03-25 03:53:42 -0300
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treefa581f6dc1c0596391690d1f67eceef3af8246dc /Documentation/power/tuxonice.txt
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- --- TuxOnIce, version 3.0 ---
-
-1. What is it?
-2. Why would you want it?
-3. What do you need to use it?
-4. Why not just use the version already in the kernel?
-5. How do you use it?
-6. What do all those entries in /sys/power/tuxonice do?
-7. How do you get support?
-8. I think I've found a bug. What should I do?
-9. When will XXX be supported?
-10 How does it work?
-11. Who wrote TuxOnIce?
-
-1. What is it?
-
- Imagine you're sitting at your computer, working away. For some reason, you
- need to turn off your computer for a while - perhaps it's time to go home
- for the day. When you come back to your computer next, you're going to want
- to carry on where you left off. Now imagine that you could push a button and
- have your computer store the contents of its memory to disk and power down.
- Then, when you next start up your computer, it loads that image back into
- memory and you can carry on from where you were, just as if you'd never
- turned the computer off. You have far less time to start up, no reopening of
- applications or finding what directory you put that file in yesterday.
- That's what TuxOnIce does.
-
- TuxOnIce has a long heritage. It began life as work by Gabor Kuti, who,
- with some help from Pavel Machek, got an early version going in 1999. The
- project was then taken over by Florent Chabaud while still in alpha version
- numbers. Nigel Cunningham came on the scene when Florent was unable to
- continue, moving the project into betas, then 1.0, 2.0 and so on up to
- the present series. During the 2.0 series, the name was contracted to
- Suspend2 and the website suspend2.net created. Beginning around July 2007,
- a transition to calling the software TuxOnIce was made, to seek to help
- make it clear that TuxOnIce is more concerned with hibernation than suspend
- to ram.
-
- Pavel Machek's swsusp code, which was merged around 2.5.17 retains the
- original name, and was essentially a fork of the beta code until Rafael
- Wysocki came on the scene in 2005 and began to improve it further.
-
-2. Why would you want it?
-
- Why wouldn't you want it?
-
- Being able to save the state of your system and quickly restore it improves
- your productivity - you get a useful system in far less time than through
- the normal boot process. You also get to be completely 'green', using zero
- power, or as close to that as possible (the computer may still provide
- minimal power to some devices, so they can initiate a power on, but that
- will be the same amount of power as would be used if you told the computer
- to shutdown.
-
-3. What do you need to use it?
-
- a. Kernel Support.
-
- i) The TuxOnIce patch.
-
- TuxOnIce is part of the Linux Kernel. This version is not part of Linus's
- 2.6 tree at the moment, so you will need to download the kernel source and
- apply the latest patch. Having done that, enable the appropriate options in
- make [menu|x]config (under Power Management Options - look for "Enhanced
- Hibernation"), compile and install your kernel. TuxOnIce works with SMP,
- Highmem, preemption, fuse filesystems, x86-32, PPC and x86_64.
-
- TuxOnIce patches are available from http://tuxonice.net.
-
- ii) Compression support.
-
- Compression support is implemented via the cryptoapi. You will therefore want
- to select any Cryptoapi transforms that you want to use on your image from
- the Cryptoapi menu while configuring your kernel. We recommend the use of the
- LZO compression method - it is very fast and still achieves good compression.
-
- You can also tell TuxOnIce to write its image to an encrypted and/or
- compressed filesystem/swap partition. In that case, you don't need to do
- anything special for TuxOnIce when it comes to kernel configuration.
-
- iii) Configuring other options.
-
- While you're configuring your kernel, try to configure as much as possible
- to build as modules. We recommend this because there are a number of drivers
- that are still in the process of implementing proper power management
- support. In those cases, the best way to work around their current lack is
- to build them as modules and remove the modules while hibernating. You might
- also bug the driver authors to get their support up to speed, or even help!
-
- b. Storage.
-
- i) Swap.
-
- TuxOnIce can store the hibernation image in your swap partition, a swap file or
- a combination thereof. Whichever combination you choose, you will probably
- want to create enough swap space to store the largest image you could have,
- plus the space you'd normally use for swap. A good rule of thumb would be
- to calculate the amount of swap you'd want without using TuxOnIce, and then
- add the amount of memory you have. This swapspace can be arranged in any way
- you'd like. It can be in one partition or file, or spread over a number. The
- only requirement is that they be active when you start a hibernation cycle.
-
- There is one exception to this requirement. TuxOnIce has the ability to turn
- on one swap file or partition at the start of hibernating and turn it back off
- at the end. If you want to ensure you have enough memory to store a image
- when your memory is fully used, you might want to make one swap partition or
- file for 'normal' use, and another for TuxOnIce to activate & deactivate
- automatically. (Further details below).
-
- ii) Normal files.
-
- TuxOnIce includes a 'file allocator'. The file allocator can store your
- image in a simple file. Since Linux has the concept of everything being a
- file, this is more powerful than it initially sounds. If, for example, you
- were to set up a network block device file, you could hibernate to a network
- server. This has been tested and works to a point, but nbd itself isn't
- stateless enough for our purposes.
-
- Take extra care when setting up the file allocator. If you just type
- commands without thinking and then try to hibernate, you could cause
- irreversible corruption on your filesystems! Make sure you have backups.
-
- Most people will only want to hibernate to a local file. To achieve that, do
- something along the lines of:
-
- echo "TuxOnIce" > /hibernation-file
- dd if=/dev/zero bs=1M count=512 >> /hibernation-file
-
- This will create a 512MB file called /hibernation-file. To get TuxOnIce to use
- it:
-
- echo /hibernation-file > /sys/power/tuxonice/file/target
-
- Then
-
- cat /sys/power/tuxonice/resume
-
- Put the results of this into your bootloader's configuration (see also step
- C, below):
-
- ---EXAMPLE-ONLY-DON'T-COPY-AND-PASTE---
- # cat /sys/power/tuxonice/resume
- file:/dev/hda2:0x1e001
-
- In this example, we would edit the append= line of our lilo.conf|menu.lst
- so that it included:
-
- resume=file:/dev/hda2:0x1e001
- ---EXAMPLE-ONLY-DON'T-COPY-AND-PASTE---
-
- For those who are thinking 'Could I make the file sparse?', the answer is
- 'No!'. At the moment, there is no way for TuxOnIce to fill in the holes in
- a sparse file while hibernating. In the longer term (post merge!), I'd like
- to change things so that the file could be dynamically resized and have
- holes filled as needed. Right now, however, that's not possible and not a
- priority.
-
- c. Bootloader configuration.
-
- Using TuxOnIce also requires that you add an extra parameter to
- your lilo.conf or equivalent. Here's an example for a swap partition:
-
- append="resume=swap:/dev/hda1"
-
- This would tell TuxOnIce that /dev/hda1 is a swap partition you
- have. TuxOnIce will use the swap signature of this partition as a
- pointer to your data when you hibernate. This means that (in this example)
- /dev/hda1 doesn't need to be _the_ swap partition where all of your data
- is actually stored. It just needs to be a swap partition that has a
- valid signature.
-
- You don't need to have a swap partition for this purpose. TuxOnIce
- can also use a swap file, but usage is a little more complex. Having made
- your swap file, turn it on and do
-
- cat /sys/power/tuxonice/swap/headerlocations
-
- (this assumes you've already compiled your kernel with TuxOnIce
- support and booted it). The results of the cat command will tell you
- what you need to put in lilo.conf:
-
- For swap partitions like /dev/hda1, simply use resume=/dev/hda1.
- For swapfile `swapfile`, use resume=swap:/dev/hda2:0x242d.
-
- If the swapfile changes for any reason (it is moved to a different
- location, it is deleted and recreated, or the filesystem is
- defragmented) then you will have to check
- /sys/power/tuxonice/swap/headerlocations for a new resume_block value.
-
- Once you've compiled and installed the kernel and adjusted your bootloader
- configuration, you should only need to reboot for the most basic part
- of TuxOnIce to be ready.
-
- If you only compile in the swap allocator, or only compile in the file
- allocator, you don't need to add the "swap:" part of the resume=
- parameters above. resume=/dev/hda2:0x242d will work just as well. If you
- have compiled both and your storage is on swap, you can also use this
- format (the swap allocator is the default allocator).
-
- When compiling your kernel, one of the options in the 'Power Management
- Support' menu, just above the 'Enhanced Hibernation (TuxOnIce)' entry is
- called 'Default resume partition'. This can be used to set a default value
- for the resume= parameter.
-
- d. The hibernate script.
-
- Since the driver model in 2.6 kernels is still being developed, you may need
- to do more than just configure TuxOnIce. Users of TuxOnIce usually start the
- process via a script which prepares for the hibernation cycle, tells the
- kernel to do its stuff and then restore things afterwards. This script might
- involve:
-
- - Switching to a text console and back if X doesn't like the video card
- status on resume.
- - Un/reloading drivers that don't play well with hibernation.
-
- Note that you might not be able to unload some drivers if there are
- processes using them. You might have to kill off processes that hold
- devices open. Hint: if your X server accesses an USB mouse, doing a
- 'chvt' to a text console releases the device and you can unload the
- module.
-
- Check out the latest script (available on tuxonice.net).
-
- e. The userspace user interface.
-
- TuxOnIce has very limited support for displaying status if you only apply
- the kernel patch - it can printk messages, but that is all. In addition,
- some of the functions mentioned in this document (such as cancelling a cycle
- or performing interactive debugging) are unavailable. To utilise these
- functions, or simply get a nice display, you need the 'userui' component.
- Userui comes in three flavours, usplash, fbsplash and text. Text should
- work on any console. Usplash and fbsplash require the appropriate
- (distro specific?) support.
-
- To utilise a userui, TuxOnIce just needs to be told where to find the
- userspace binary:
-
- echo "/usr/local/sbin/tuxoniceui_fbsplash" > /sys/power/tuxonice/user_interface/program
-
- The hibernate script can do this for you, and a default value for this
- setting can be configured when compiling the kernel. This path is also
- stored in the image header, so if you have an initrd or initramfs, you can
- use the userui during the first part of resuming (prior to the atomic
- restore) by putting the binary in the same path in your initrd/ramfs.
- Alternatively, you can put it in a different location and do an echo
- similar to the above prior to the echo > do_resume. The value saved in the
- image header will then be ignored.
-
-4. Why not just use the version already in the kernel?
-
- The version in the vanilla kernel has a number of drawbacks. The most
- serious of these are:
- - it has a maximum image size of 1/2 total memory;
- - it doesn't allocate storage until after it has snapshotted memory.
- This means that you can't be sure hibernating will work until you
- see it start to write the image;
- - it does not allow you to press escape to cancel a cycle;
- - it does not allow you to press escape to cancel resuming;
- - it does not allow you to automatically swapon a file when
- starting a cycle;
- - it does not allow you to use multiple swap partitions or files;
- - it does not allow you to use ordinary files;
- - it just invalidates an image and continues to boot if you
- accidentally boot the wrong kernel after hibernating;
- - it doesn't support any sort of nice display while hibernating;
- - it is moving toward requiring that you have an initrd/initramfs
- to ever have a hope of resuming (uswsusp). While uswsusp will
- address some of the concerns above, it won't address all of them,
- and will be more complicated to get set up;
- - it doesn't have support for suspend-to-both (write a hibernation
- image, then suspend to ram; I think this is known as ReadySafe
- under M$).
-
-5. How do you use it?
-
- A hibernation cycle can be started directly by doing:
-
- echo > /sys/power/tuxonice/do_hibernate
-
- In practice, though, you'll probably want to use the hibernate script
- to unload modules, configure the kernel the way you like it and so on.
- In that case, you'd do (as root):
-
- hibernate
-
- See the hibernate script's man page for more details on the options it
- takes.
-
- If you're using the text or splash user interface modules, one feature of
- TuxOnIce that you might find useful is that you can press Escape at any time
- during hibernating, and the process will be aborted.
-
- Due to the way hibernation works, this means you'll have your system back and
- perfectly usable almost instantly. The only exception is when it's at the
- very end of writing the image. Then it will need to reload a small (usually
- 4-50MBs, depending upon the image characteristics) portion first.
-
- Likewise, when resuming, you can press escape and resuming will be aborted.
- The computer will then powerdown again according to settings at that time for
- the powerdown method or rebooting.
-
- You can change the settings for powering down while the image is being
- written by pressing 'R' to toggle rebooting and 'O' to toggle between
- suspending to ram and powering down completely).
-
- If you run into problems with resuming, adding the "noresume" option to
- the kernel command line will let you skip the resume step and recover your
- system. This option shouldn't normally be needed, because TuxOnIce modifies
- the image header prior to the atomic restore, and will thus prompt you
- if it detects that you've tried to resume an image before (this flag is
- removed if you press Escape to cancel a resume, so you won't be prompted
- then).
-
- Recent kernels (2.6.24 onwards) add support for resuming from a different
- kernel to the one that was hibernated (thanks to Rafael for his work on
- this - I've just embraced and enhanced the support for TuxOnIce). This
- should further reduce the need for you to use the noresume option.
-
-6. What do all those entries in /sys/power/tuxonice do?
-
- /sys/power/tuxonice is the directory which contains files you can use to
- tune and configure TuxOnIce to your liking. The exact contents of
- the directory will depend upon the version of TuxOnIce you're
- running and the options you selected at compile time. In the following
- descriptions, names in brackets refer to compile time options.
- (Note that they're all dependant upon you having selected CONFIG_TUXONICE
- in the first place!).
-
- Since the values of these settings can open potential security risks, the
- writeable ones are accessible only to the root user. You may want to
- configure sudo to allow you to invoke your hibernate script as an ordinary
- user.
-
- - alloc/failure_test
-
- This debugging option provides a way of testing TuxOnIce's handling of
- memory allocation failures. Each allocation type that TuxOnIce makes has
- been given a unique number (see the source code). Echo the appropriate
- number into this entry, and when TuxOnIce attempts to do that allocation,
- it will pretend there was a failure and act accordingly.
-
- - alloc/find_max_mem_allocated
-
- This debugging option will cause TuxOnIce to find the maximum amount of
- memory it used during a cycle, and report that information in debugging
- information at the end of the cycle.
-
- - alt_resume_param
-
- Instead of powering down after writing a hibernation image, TuxOnIce
- supports resuming from a different image. This entry lets you set the
- location of the signature for that image (the resume= value you'd use
- for it). Using an alternate image and keep_image mode, you can do things
- like using an alternate image to power down an uninterruptible power
- supply.
-
- - block_io/target_outstanding_io
-
- This value controls the amount of memory that the block I/O code says it
- needs when the core code is calculating how much memory is needed for
- hibernating and for resuming. It doesn't directly control the amount of
- I/O that is submitted at any one time - that depends on the amount of
- available memory (we may have more available than we asked for), the
- throughput that is being achieved and the ability of the CPU to keep up
- with disk throughput (particularly where we're compressing pages).
-
- - checksum/enabled
-
- Use cryptoapi hashing routines to verify that Pageset2 pages don't change
- while we're saving the first part of the image, and to get any pages that
- do change resaved in the atomic copy. This should normally not be needed,
- but if you're seeing issues, please enable this. If your issues stop you
- being able to resume, enable this option, hibernate and cancel the cycle
- after the atomic copy is done. If the debugging info shows a non-zero
- number of pages resaved, please report this to Nigel.
-
- - compression/algorithm
-
- Set the cryptoapi algorithm used for compressing the image.
-
- - compression/expected_compression
-
- These values allow you to set an expected compression ratio, which TuxOnice
- will use in calculating whether it meets constraints on the image size. If
- this expected compression ratio is not attained, the hibernation cycle will
- abort, so it is wise to allow some spare. You can see what compression
- ratio is achieved in the logs after hibernating.
-
- - debug_info:
-
- This file returns information about your configuration that may be helpful
- in diagnosing problems with hibernating.
-
- - did_suspend_to_both:
-
- This file can be used when you hibernate with powerdown method 3 (ie suspend
- to ram after writing the image). There can be two outcomes in this case. We
- can resume from the suspend-to-ram before the battery runs out, or we can run
- out of juice and and up resuming like normal. This entry lets you find out,
- post resume, which way we went. If the value is 1, we resumed from suspend
- to ram. This can be useful when actions need to be run post suspend-to-ram
- that don't need to be run if we did the normal resume from power off.
-
- - do_hibernate:
-
- When anything is written to this file, the kernel side of TuxOnIce will
- begin to attempt to write an image to disk and power down. You'll normally
- want to run the hibernate script instead, to get modules unloaded first.
-
- - do_resume:
-
- When anything is written to this file TuxOnIce will attempt to read and
- restore an image. If there is no image, it will return almost immediately.
- If an image exists, the echo > will never return. Instead, the original
- kernel context will be restored and the original echo > do_hibernate will
- return.
-
- - */enabled
-
- These option can be used to temporarily disable various parts of TuxOnIce.
-
- - extra_pages_allowance
-
- When TuxOnIce does its atomic copy, it calls the driver model suspend
- and resume methods. If you have DRI enabled with a driver such as fglrx,
- this can result in the driver allocating a substantial amount of memory
- for storing its state. Extra_pages_allowance tells TuxOnIce how much
- extra memory it should ensure is available for those allocations. If
- your attempts at hibernating end with a message in dmesg indicating that
- insufficient extra pages were allowed, you need to increase this value.
-
- - file/target:
-
- Read this value to get the current setting. Write to it to point TuxOnice
- at a new storage location for the file allocator. See section 3.b.ii above
- for details of how to set up the file allocator.
-
- - freezer_test
-
- This entry can be used to get TuxOnIce to just test the freezer and prepare
- an image without actually doing a hibernation cycle. It is useful for
- diagnosing freezing and image preparation issues.
-
- - full_pageset2
-
- TuxOnIce divides the pages that are stored in an image into two sets. The
- difference between the two sets is that pages in pageset 1 are atomically
- copied, and pages in pageset 2 are written to disk without being copied
- first. A page CAN be written to disk without being copied first if and only
- if its contents will not be modified or used at any time after userspace
- processes are frozen. A page MUST be in pageset 1 if its contents are
- modified or used at any time after userspace processes have been frozen.
-
- Normally (ie if this option is enabled), TuxOnIce will put all pages on the
- per-zone LRUs in pageset2, then remove those pages used by any userspace
- user interface helper and TuxOnIce storage manager that are running,
- together with pages used by the GEM memory manager introduced around 2.6.28
- kernels.
-
- If this option is disabled, a much more conservative approach will be taken.
- The only pages in pageset2 will be those belonging to userspace processes,
- with the exclusion of those belonging to the TuxOnIce userspace helpers
- mentioned above. This will result in a much smaller pageset2, and will
- therefore result in smaller images than are possible with this option
- enabled.
-
- - ignore_rootfs
-
- TuxOnIce records which device is mounted as the root filesystem when
- writing the hibernation image. It will normally check at resume time that
- this device isn't already mounted - that would be a cause of filesystem
- corruption. In some particular cases (RAM based root filesystems), you
- might want to disable this check. This option allows you to do that.
-
- - image_exists:
-
- Can be used in a script to determine whether a valid image exists at the
- location currently pointed to by resume=. Returns up to three lines.
- The first is whether an image exists (-1 for unsure, otherwise 0 or 1).
- If an image eixsts, additional lines will return the machine and version.
- Echoing anything to this entry removes any current image.
-
- - image_size_limit:
-
- The maximum size of hibernation image written to disk, measured in megabytes
- (1024*1024).
-
- - last_result:
-
- The result of the last hibernation cycle, as defined in
- include/linux/suspend-debug.h with the values SUSPEND_ABORTED to
- SUSPEND_KEPT_IMAGE. This is a bitmask.
-
- - late_cpu_hotplug:
-
- This sysfs entry controls whether cpu hotplugging is done - as normal - just
- before (unplug) and after (replug) the atomic copy/restore (so that all
- CPUs/cores are available for multithreaded I/O). The alternative is to
- unplug all secondary CPUs/cores at the start of hibernating/resuming, and
- replug them at the end of resuming. No multithreaded I/O will be possible in
- this configuration, but the odd machine has been reported to require it.
-
- - lid_file:
-
- This determines which ACPI button file we look in to determine whether the
- lid is open or closed after resuming from suspend to disk or power off.
- If the entry is set to "lid/LID", we'll open /proc/acpi/button/lid/LID/state
- and check its contents at the appropriate moment. See post_wake_state below
- for more details on how this entry is used.
-
- - log_everything (CONFIG_PM_DEBUG):
-
- Setting this option results in all messages printed being logged. Normally,
- only a subset are logged, so as to not slow the process and not clutter the
- logs. Useful for debugging. It can be toggled during a cycle by pressing
- 'L'.
-
- - no_load_direct:
-
- This is a debugging option. If, when loading the atomically copied pages of
- an image, TuxOnIce finds that the destination address for a page is free,
- it will normally allocate the image, load the data directly into that
- address and skip it in the atomic restore. If this option is disabled, the
- page will be loaded somewhere else and atomically restored like other pages.
-
- - no_flusher_thread:
-
- When doing multithreaded I/O (see below), the first online CPU can be used
- to _just_ submit compressed pages when writing the image, rather than
- compressing and submitting data. This option is normally disabled, but has
- been included because Nigel would like to see whether it will be more useful
- as the number of cores/cpus in computers increases.
-
- - no_multithreaded_io:
-
- TuxOnIce will normally create one thread per cpu/core on your computer,
- each of which will then perform I/O. This will generally result in
- throughput that's the maximum the storage medium can handle. There
- shouldn't be any reason to disable multithreaded I/O now, but this option
- has been retained for debugging purposes.
-
- - no_pageset2
-
- See the entry for full_pageset2 above for an explanation of pagesets.
- Enabling this option causes TuxOnIce to do an atomic copy of all pages,
- thereby limiting the maximum image size to 1/2 of memory, as swsusp does.
-
- - no_pageset2_if_unneeded
-
- See the entry for full_pageset2 above for an explanation of pagesets.
- Enabling this option causes TuxOnIce to act like no_pageset2 was enabled
- if and only it isn't needed anyway. This option may still make TuxOnIce
- less reliable because pageset2 pages are normally used to store the
- atomic copy - drivers that want to do allocations of larger amounts of
- memory in one shot will be more likely to find that those amounts aren't
- available if this option is enabled.
-
- - pause_between_steps (CONFIG_PM_DEBUG):
-
- This option is used during debugging, to make TuxOnIce pause between
- each step of the process. It is ignored when the nice display is on.
-
- - post_wake_state:
-
- TuxOnIce provides support for automatically waking after a user-selected
- delay, and using a different powerdown method if the lid is still closed.
- (Yes, we're assuming a laptop). This entry lets you choose what state
- should be entered next. The values are those described under
- powerdown_method, below. It can be used to suspend to RAM after hibernating,
- then powerdown properly (say) 20 minutes. It can also be used to power down
- properly, then wake at (say) 6.30am and suspend to RAM until you're ready
- to use the machine.
-
- - powerdown_method:
-
- Used to select a method by which TuxOnIce should powerdown after writing the
- image. Currently:
-
- 0: Don't use ACPI to power off.
- 3: Attempt to enter Suspend-to-ram.
- 4: Attempt to enter ACPI S4 mode.
- 5: Attempt to power down via ACPI S5 mode.
-
- Note that these options are highly dependant upon your hardware & software:
-
- 3: When succesful, your machine suspends to ram instead of powering off.
- The advantage of using this mode is that it doesn't matter whether your
- battery has enough charge to make it through to your next resume. If it
- lasts, you will simply resume from suspend to ram (and the image on disk
- will be discarded). If the battery runs out, you will resume from disk
- instead. The disadvantage is that it takes longer than a normal
- suspend-to-ram to enter the state, since the suspend-to-disk image needs
- to be written first.
- 4/5: When successful, your machine will be off and comsume (almost) no power.
- But it might still react to some external events like opening the lid or
- trafic on a network or usb device. For the bios, resume is then the same
- as warm boot, similar to a situation where you used the command `reboot'
- to reboot your machine. If your machine has problems on warm boot or if
- you want to protect your machine with the bios password, this is probably
- not the right choice. Mode 4 may be necessary on some machines where ACPI
- wake up methods need to be run to properly reinitialise hardware after a
- hibernation cycle.
- 0: Switch the machine completely off. The only possible wakeup is the power
- button. For the bios, resume is then the same as a cold boot, in
- particular you would have to provide your bios boot password if your
- machine uses that feature for booting.
-
- - progressbar_granularity_limit:
-
- This option can be used to limit the granularity of the progress bar
- displayed with a bootsplash screen. The value is the maximum number of
- steps. That is, 10 will make the progress bar jump in 10% increments.
-
- - reboot:
-
- This option causes TuxOnIce to reboot rather than powering down
- at the end of saving an image. It can be toggled during a cycle by pressing
- 'R'.
-
- - resume:
-
- This sysfs entry can be used to read and set the location in which TuxOnIce
- will look for the signature of an image - the value set using resume= at
- boot time or CONFIG_PM_STD_PARTITION ("Default resume partition"). By
- writing to this file as well as modifying your bootloader's configuration
- file (eg menu.lst), you can set or reset the location of your image or the
- method of storing the image without rebooting.
-
- - replace_swsusp (CONFIG_TOI_REPLACE_SWSUSP):
-
- This option makes
-
- echo disk > /sys/power/state
-
- activate TuxOnIce instead of swsusp. Regardless of whether this option is
- enabled, any invocation of swsusp's resume time trigger will cause TuxOnIce
- to check for an image too. This is due to the fact that at resume time, we
- can't know whether this option was enabled until we see if an image is there
- for us to resume from. (And when an image exists, we don't care whether we
- did replace swsusp anyway - we just want to resume).
-
- - resume_commandline:
-
- This entry can be read after resuming to see the commandline that was used
- when resuming began. You might use this to set up two bootloader entries
- that are the same apart from the fact that one includes a extra append=
- argument "at_work=1". You could then grep resume_commandline in your
- post-resume scripts and configure networking (for example) differently
- depending upon whether you're at home or work. resume_commandline can be
- set to arbitrary text if you wish to remove sensitive contents.
-
- - swap/swapfilename:
-
- This entry is used to specify the swapfile or partition that
- TuxOnIce will attempt to swapon/swapoff automatically. Thus, if
- I normally use /dev/hda1 for swap, and want to use /dev/hda2 for specifically
- for my hibernation image, I would
-
- echo /dev/hda2 > /sys/power/tuxonice/swap/swapfile
-
- /dev/hda2 would then be automatically swapon'd and swapoff'd. Note that the
- swapon and swapoff occur while other processes are frozen (including kswapd)
- so this swap file will not be used up when attempting to free memory. The
- parition/file is also given the highest priority, so other swapfiles/partitions
- will only be used to save the image when this one is filled.
-
- The value of this file is used by headerlocations along with any currently
- activated swapfiles/partitions.
-
- - swap/headerlocations:
-
- This option tells you the resume= options to use for swap devices you
- currently have activated. It is particularly useful when you only want to
- use a swap file to store your image. See above for further details.
-
- - test_bio
-
- This is a debugging option. When enabled, TuxOnIce will not hibernate.
- Instead, when asked to write an image, it will skip the atomic copy,
- just doing the writing of the image and then returning control to the
- user at the point where it would have powered off. This is useful for
- testing throughput in different configurations.
-
- - test_filter_speed
-
- This is a debugging option. When enabled, TuxOnIce will not hibernate.
- Instead, when asked to write an image, it will not write anything or do
- an atomic copy, but will only run any enabled compression algorithm on the
- data that would have been written (the source pages of the atomic copy in
- the case of pageset 1). This is useful for comparing the performance of
- compression algorithms and for determining the extent to which an upgrade
- to your storage method would improve hibernation speed.
-
- - user_interface/debug_sections (CONFIG_PM_DEBUG):
-
- This value, together with the console log level, controls what debugging
- information is displayed. The console log level determines the level of
- detail, and this value determines what detail is displayed. This value is
- a bit vector, and the meaning of the bits can be found in the kernel tree
- in include/linux/tuxonice.h. It can be overridden using the kernel's
- command line option suspend_dbg.
-
- - user_interface/default_console_level (CONFIG_PM_DEBUG):
-
- This determines the value of the console log level at the start of a
- hibernation cycle. If debugging is compiled in, the console log level can be
- changed during a cycle by pressing the digit keys. Meanings are:
-
- 0: Nice display.
- 1: Nice display plus numerical progress.
- 2: Errors only.
- 3: Low level debugging info.
- 4: Medium level debugging info.
- 5: High level debugging info.
- 6: Verbose debugging info.
-
- - user_interface/enable_escape:
-
- Setting this to "1" will enable you abort a hibernation cycle or resuming by
- pressing escape, "0" (default) disables this feature. Note that enabling
- this option means that you cannot initiate a hibernation cycle and then walk
- away from your computer, expecting it to be secure. With feature disabled,
- you can validly have this expectation once TuxOnice begins to write the
- image to disk. (Prior to this point, it is possible that TuxOnice might
- about because of failure to freeze all processes or because constraints
- on its ability to save the image are not met).
-
- - user_interface/program
-
- This entry is used to tell TuxOnice what userspace program to use for
- providing a user interface while hibernating. The program uses a netlink
- socket to pass messages back and forward to the kernel, allowing all of the
- functions formerly implemented in the kernel user interface components.
-
- - version:
-
- The version of TuxOnIce you have compiled into the currently running kernel.
-
- - wake_alarm_dir:
-
- As mentioned above (post_wake_state), TuxOnIce supports automatically waking
- after some delay. This entry allows you to select which wake alarm to use.
- It should contain the value "rtc0" if you're wanting to use
- /sys/class/rtc/rtc0.
-
- - wake_delay:
-
- This value determines the delay from the end of writing the image until the
- wake alarm is triggered. You can set an absolute time by writing the desired
- time into /sys/class/rtc/<wake_alarm_dir>/wakealarm and leaving these values
- empty.
-
- Note that for the wakeup to actually occur, you may need to modify entries
- in /proc/acpi/wakeup. This is done by echoing the name of the button in the
- first column (eg PBTN) into the file.
-
-7. How do you get support?
-
- Glad you asked. TuxOnIce is being actively maintained and supported
- by Nigel (the guy doing most of the kernel coding at the moment), Bernard
- (who maintains the hibernate script and userspace user interface components)
- and its users.
-
- Resources availble include HowTos, FAQs and a Wiki, all available via
- tuxonice.net. You can find the mailing lists there.
-
-8. I think I've found a bug. What should I do?
-
- By far and a way, the most common problems people have with TuxOnIce
- related to drivers not having adequate power management support. In this
- case, it is not a bug with TuxOnIce, but we can still help you. As we
- mentioned above, such issues can usually be worked around by building the
- functionality as modules and unloading them while hibernating. Please visit
- the Wiki for up-to-date lists of known issues and work arounds.
-
- If this information doesn't help, try running:
-
- hibernate --bug-report
-
- ..and sending the output to the users mailing list.
-
- Good information on how to provide us with useful information from an
- oops is found in the file REPORTING-BUGS, in the top level directory
- of the kernel tree. If you get an oops, please especially note the
- information about running what is printed on the screen through ksymoops.
- The raw information is useless.
-
-9. When will XXX be supported?
-
- If there's a feature missing from TuxOnIce that you'd like, feel free to
- ask. We try to be obliging, within reason.
-
- Patches are welcome. Please send to the list.
-
-10. How does it work?
-
- TuxOnIce does its work in a number of steps.
-
- a. Freezing system activity.
-
- The first main stage in hibernating is to stop all other activity. This is
- achieved in stages. Processes are considered in fours groups, which we will
- describe in reverse order for clarity's sake: Threads with the PF_NOFREEZE
- flag, kernel threads without this flag, userspace processes with the
- PF_SYNCTHREAD flag and all other processes. The first set (PF_NOFREEZE) are
- untouched by the refrigerator code. They are allowed to run during hibernating
- and resuming, and are used to support user interaction, storage access or the
- like. Other kernel threads (those unneeded while hibernating) are frozen last.
- This leaves us with userspace processes that need to be frozen. When a
- process enters one of the *_sync system calls, we set a PF_SYNCTHREAD flag on
- that process for the duration of that call. Processes that have this flag are
- frozen after processes without it, so that we can seek to ensure that dirty
- data is synced to disk as quickly as possible in a situation where other
- processes may be submitting writes at the same time. Freezing the processes
- that are submitting data stops new I/O from being submitted. Syncthreads can
- then cleanly finish their work. So the order is:
-
- - Userspace processes without PF_SYNCTHREAD or PF_NOFREEZE;
- - Userspace processes with PF_SYNCTHREAD (they won't have NOFREEZE);
- - Kernel processes without PF_NOFREEZE.
-
- b. Eating memory.
-
- For a successful hibernation cycle, you need to have enough disk space to store the
- image and enough memory for the various limitations of TuxOnIce's
- algorithm. You can also specify a maximum image size. In order to attain
- to those constraints, TuxOnIce may 'eat' memory. If, after freezing
- processes, the constraints aren't met, TuxOnIce will thaw all the
- other processes and begin to eat memory until its calculations indicate
- the constraints are met. It will then freeze processes again and recheck
- its calculations.
-
- c. Allocation of storage.
-
- Next, TuxOnIce allocates the storage that will be used to save
- the image.
-
- The core of TuxOnIce knows nothing about how or where pages are stored. We
- therefore request the active allocator (remember you might have compiled in
- more than one!) to allocate enough storage for our expect image size. If
- this request cannot be fulfilled, we eat more memory and try again. If it
- is fulfiled, we seek to allocate additional storage, just in case our
- expected compression ratio (if any) isn't achieved. This time, however, we
- just continue if we can't allocate enough storage.
-
- If these calls to our allocator change the characteristics of the image
- such that we haven't allocated enough memory, we also loop. (The allocator
- may well need to allocate space for its storage information).
-
- d. Write the first part of the image.
-
- TuxOnIce stores the image in two sets of pages called 'pagesets'.
- Pageset 2 contains pages on the active and inactive lists; essentially
- the page cache. Pageset 1 contains all other pages, including the kernel.
- We use two pagesets for one important reason: We need to make an atomic copy
- of the kernel to ensure consistency of the image. Without a second pageset,
- that would limit us to an image that was at most half the amount of memory
- available. Using two pagesets allows us to store a full image. Since pageset
- 2 pages won't be needed in saving pageset 1, we first save pageset 2 pages.
- We can then make our atomic copy of the remaining pages using both pageset 2
- pages and any other pages that are free. While saving both pagesets, we are
- careful not to corrupt the image. Among other things, we use lowlevel block
- I/O routines that don't change the pagecache contents.
-
- The next step, then, is writing pageset 2.
-
- e. Suspending drivers and storing processor context.
-
- Having written pageset2, TuxOnIce calls the power management functions to
- notify drivers of the hibernation, and saves the processor state in preparation
- for the atomic copy of memory we are about to make.
-
- f. Atomic copy.
-
- At this stage, everything else but the TuxOnIce code is halted. Processes
- are frozen or idling, drivers are quiesced and have stored (ideally and where
- necessary) their configuration in memory we are about to atomically copy.
- In our lowlevel architecture specific code, we have saved the CPU state.
- We can therefore now do our atomic copy before resuming drivers etc.
-
- g. Save the atomic copy (pageset 1).
-
- TuxOnice can then write the atomic copy of the remaining pages. Since we
- have copied the pages into other locations, we can continue to use the
- normal block I/O routines without fear of corruption our image.
-
- f. Save the image header.
-
- Nearly there! We save our settings and other parameters needed for
- reloading pageset 1 in an 'image header'. We also tell our allocator to
- serialise its data at this stage, so that it can reread the image at resume
- time.
-
- g. Set the image header.
-
- Finally, we edit the header at our resume= location. The signature is
- changed by the allocator to reflect the fact that an image exists, and to
- point to the start of that data if necessary (swap allocator).
-
- h. Power down.
-
- Or reboot if we're debugging and the appropriate option is selected.
-
- Whew!
-
- Reloading the image.
- --------------------
-
- Reloading the image is essentially the reverse of all the above. We load
- our copy of pageset 1, being careful to choose locations that aren't going
- to be overwritten as we copy it back (We start very early in the boot
- process, so there are no other processes to quiesce here). We then copy
- pageset 1 back to its original location in memory and restore the process
- context. We are now running with the original kernel. Next, we reload the
- pageset 2 pages, free the memory and swap used by TuxOnIce, restore
- the pageset header and restart processes. Sounds easy in comparison to
- hibernating, doesn't it!
-
- There is of course more to TuxOnIce than this, but this explanation
- should be a good start. If there's interest, I'll write further
- documentation on range pages and the low level I/O.
-
-11. Who wrote TuxOnIce?
-
- (Answer based on the writings of Florent Chabaud, credits in files and
- Nigel's limited knowledge; apologies to anyone missed out!)
-
- The main developers of TuxOnIce have been...
-
- Gabor Kuti
- Pavel Machek
- Florent Chabaud
- Bernard Blackham
- Nigel Cunningham
-
- Significant portions of swsusp, the code in the vanilla kernel which
- TuxOnIce enhances, have been worked on by Rafael Wysocki. Thanks should
- also be expressed to him.
-
- The above mentioned developers have been aided in their efforts by a host
- of hundreds, if not thousands of testers and people who have submitted bug
- fixes & suggestions. Of special note are the efforts of Michael Frank, who
- had his computers repetitively hibernate and resume for literally tens of
- thousands of cycles and developed scripts to stress the system and test
- TuxOnIce far beyond the point most of us (Nigel included!) would consider
- testing. His efforts have contributed as much to TuxOnIce as any of the
- names above.