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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
commit03dd4cb26d967f9588437b0fc9cc0e8353322bb7 (patch)
treefa581f6dc1c0596391690d1f67eceef3af8246dc /Documentation/power
parentd4e493caf788ef44982e131ff9c786546904d934 (diff)
Linux-libre 4.5-gnu
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/pci.txt2
-rw-r--r--Documentation/power/runtime_pm.txt6
-rw-r--r--Documentation/power/tuxonice-internals.txt532
-rw-r--r--Documentation/power/tuxonice.txt948
4 files changed, 7 insertions, 1481 deletions
diff --git a/Documentation/power/pci.txt b/Documentation/power/pci.txt
index b0e911e0e..44558882a 100644
--- a/Documentation/power/pci.txt
+++ b/Documentation/power/pci.txt
@@ -999,7 +999,7 @@ from its probe routine to make runtime PM work for the device.
It is important to remember that the driver's runtime_suspend() callback
may be executed right after the usage counter has been decremented, because
-user space may already have cuased the pm_runtime_allow() helper function
+user space may already have caused the pm_runtime_allow() helper function
unblocking the runtime PM of the device to run via sysfs, so the driver must
be prepared to cope with that.
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 0784bc3a2..7328cf852 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -371,6 +371,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
- increment the device's usage counter, run pm_runtime_resume(dev) and
return its result
+ int pm_runtime_get_if_in_use(struct device *dev);
+ - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
+ runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
+ nonzero, increment the counter and return 1; otherwise return 0 without
+ changing the counter
+
void pm_runtime_put_noidle(struct device *dev);
- decrement the device's usage counter
diff --git a/Documentation/power/tuxonice-internals.txt b/Documentation/power/tuxonice-internals.txt
deleted file mode 100644
index 0c6a2163a..000000000
--- a/Documentation/power/tuxonice-internals.txt
+++ /dev/null
@@ -1,532 +0,0 @@
- TuxOnIce 4.0 Internal Documentation.
- Updated to 23 March 2015
-
-(Please note that incremental image support mentioned in this document is work
-in progress. This document may need updating prior to the actual release of
-4.0!)
-
-1. Introduction.
-
- TuxOnIce 4.0 is an addition to the Linux Kernel, designed to
- allow the user to quickly shutdown and quickly boot a computer, without
- needing to close documents or programs. It is equivalent to the
- hibernate facility in some laptops. This implementation, however,
- requires no special BIOS or hardware support.
-
- The code in these files is based upon the original implementation
- prepared by Gabor Kuti and additional work by Pavel Machek and a
- host of others. This code has been substantially reworked by Nigel
- Cunningham, again with the help and testing of many others, not the
- least of whom are Bernard Blackham and Michael Frank. At its heart,
- however, the operation is essentially the same as Gabor's version.
-
-2. Overview of operation.
-
- The basic sequence of operations is as follows:
-
- a. Quiesce all other activity.
- b. Ensure enough memory and storage space are available, and attempt
- to free memory/storage if necessary.
- c. Allocate the required memory and storage space.
- d. Write the image.
- e. Power down.
-
- There are a number of complicating factors which mean that things are
- not as simple as the above would imply, however...
-
- o The activity of each process must be stopped at a point where it will
- not be holding locks necessary for saving the image, or unexpectedly
- restart operations due to something like a timeout and thereby make
- our image inconsistent.
-
- o It is desirous that we sync outstanding I/O to disk before calculating
- image statistics. This reduces corruption if one should suspend but
- then not resume, and also makes later parts of the operation safer (see
- below).
-
- o We need to get as close as we can to an atomic copy of the data.
- Inconsistencies in the image will result in inconsistent memory contents at
- resume time, and thus in instability of the system and/or file system
- corruption. This would appear to imply a maximum image size of one half of
- the amount of RAM, but we have a solution... (again, below).
-
- o In 2.6 and later, we choose to play nicely with the other suspend-to-disk
- implementations.
-
-3. Detailed description of internals.
-
- a. Quiescing activity.
-
- Safely quiescing the system is achieved using three separate but related
- aspects.
-
- First, we use the vanilla kerne's support for freezing processes. This code
- is based on the observation that the vast majority of processes don't need
- to run during suspend. They can be 'frozen'. The kernel therefore
- implements a refrigerator routine, which processes enter and in which they
- remain until the cycle is complete. Processes enter the refrigerator via
- try_to_freeze() invocations at appropriate places. A process cannot be
- frozen in any old place. It must not be holding locks that will be needed
- for writing the image or freezing other processes. For this reason,
- userspace processes generally enter the refrigerator via the signal
- handling code, and kernel threads at the place in their event loops where
- they drop locks and yield to other processes or sleep. The task of freezing
- processes is complicated by the fact that there can be interdependencies
- between processes. Freezing process A before process B may mean that
- process B cannot be frozen, because it stops at waiting for process A
- rather than in the refrigerator. This issue is seen where userspace waits
- on freezeable kernel threads or fuse filesystem threads. To address this
- issue, we implement the following algorithm for quiescing activity:
-
- - Freeze filesystems (including fuse - userspace programs starting
- new requests are immediately frozen; programs already running
- requests complete their work before being frozen in the next
- step)
- - Freeze userspace
- - Thaw filesystems (this is safe now that userspace is frozen and no
- fuse requests are outstanding).
- - Invoke sys_sync (noop on fuse).
- - Freeze filesystems
- - Freeze kernel threads
-
- If we need to free memory, we thaw kernel threads and filesystems, but not
- userspace. We can then free caches without worrying about deadlocks due to
- swap files being on frozen filesystems or such like.
-
- b. Ensure enough memory & storage are available.
-
- We have a number of constraints to meet in order to be able to successfully
- suspend and resume.
-
- First, the image will be written in two parts, described below. One of
- these parts needs to have an atomic copy made, which of course implies a
- maximum size of one half of the amount of system memory. The other part
- ('pageset') is not atomically copied, and can therefore be as large or
- small as desired.
-
- Second, we have constraints on the amount of storage available. In these
- calculations, we may also consider any compression that will be done. The
- cryptoapi module allows the user to configure an expected compression ratio.
-
- Third, the user can specify an arbitrary limit on the image size, in
- megabytes. This limit is treated as a soft limit, so that we don't fail the
- attempt to suspend if we cannot meet this constraint.
-
- c. Allocate the required memory and storage space.
-
- Having done the initial freeze, we determine whether the above constraints
- are met, and seek to allocate the metadata for the image. If the constraints
- are not met, or we fail to allocate the required space for the metadata, we
- seek to free the amount of memory that we calculate is needed and try again.
- We allow up to four iterations of this loop before aborting the cycle. If
- we do fail, it should only be because of a bug in TuxOnIce's calculations
- or the vanilla kernel code for freeing memory.
-
- These steps are merged together in the prepare_image function, found in
- prepare_image.c. The functions are merged because of the cyclical nature
- of the problem of calculating how much memory and storage is needed. Since
- the data structures containing the information about the image must
- themselves take memory and use storage, the amount of memory and storage
- required changes as we prepare the image. Since the changes are not large,
- only one or two iterations will be required to achieve a solution.
-
- The recursive nature of the algorithm is miminised by keeping user space
- frozen while preparing the image, and by the fact that our records of which
- pages are to be saved and which pageset they are saved in use bitmaps (so
- that changes in number or fragmentation of the pages to be saved don't
- feedback via changes in the amount of memory needed for metadata). The
- recursiveness is thus limited to any extra slab pages allocated to store the
- extents that record storage used, and the effects of seeking to free memory.
-
- d. Write the image.
-
- We previously mentioned the need to create an atomic copy of the data, and
- the half-of-memory limitation that is implied in this. This limitation is
- circumvented by dividing the memory to be saved into two parts, called
- pagesets.
-
- Pageset2 contains most of the page cache - the pages on the active and
- inactive LRU lists that aren't needed or modified while TuxOnIce is
- running, so they can be safely written without an atomic copy. They are
- therefore saved first and reloaded last. While saving these pages,
- TuxOnIce carefully ensures that the work of writing the pages doesn't make
- the image inconsistent. With the support for Kernel (Video) Mode Setting
- going into the kernel at the time of writing, we need to check for pages
- on the LRU that are used by KMS, and exclude them from pageset2. They are
- atomically copied as part of pageset 1.
-
- Once pageset2 has been saved, we prepare to do the atomic copy of remaining
- memory. As part of the preparation, we power down drivers, thereby providing
- them with the opportunity to have their state recorded in the image. The
- amount of memory allocated by drivers for this is usually negligible, but if
- DRI is in use, video drivers may require significants amounts. Ideally we
- would be able to query drivers while preparing the image as to the amount of
- memory they will need. Unfortunately no such mechanism exists at the time of
- writing. For this reason, TuxOnIce allows the user to set an
- 'extra_pages_allowance', which is used to seek to ensure sufficient memory
- is available for drivers at this point. TuxOnIce also lets the user set this
- value to 0. In this case, a test driver suspend is done while preparing the
- image, and the difference (plus a margin) used instead. TuxOnIce will also
- automatically restart the hibernation process (twice at most) if it finds
- that the extra pages allowance is not sufficient. It will then use what was
- actually needed (plus a margin, again). Failure to hibernate should thus
- be an extremely rare occurence.
-
- Having suspended the drivers, we save the CPU context before making an
- atomic copy of pageset1, resuming the drivers and saving the atomic copy.
- After saving the two pagesets, we just need to save our metadata before
- powering down.
-
- As we mentioned earlier, the contents of pageset2 pages aren't needed once
- they've been saved. We therefore use them as the destination of our atomic
- copy. In the unlikely event that pageset1 is larger, extra pages are
- allocated while the image is being prepared. This is normally only a real
- possibility when the system has just been booted and the page cache is
- small.
-
- This is where we need to be careful about syncing, however. Pageset2 will
- probably contain filesystem meta data. If this is overwritten with pageset1
- and then a sync occurs, the filesystem will be corrupted - at least until
- resume time and another sync of the restored data. Since there is a
- possibility that the user might not resume or (may it never be!) that
- TuxOnIce might oops, we do our utmost to avoid syncing filesystems after
- copying pageset1.
-
- e. Incremental images
-
- TuxOnIce 4.0 introduces a new incremental image mode which changes things a
- little. When incremental images are enabled, we save a 'normal' image the
- first time we hibernate. One resume however, we do not free the image or
- the associated storage. Instead, it is retained until the next attempt at
- hibernating and a mechanism is enabled which is used to track which pages
- of memory are modified between the two cycles. The modified pages can then
- be added to the existing image, rather than unmodified pages being saved
- again unnecessarily.
-
- Incremental image support is available in 64 bit Linux only, due to the
- requirement for extra page flags.
-
- This support is accomplished in the following way:
-
- 1) Tracking of pages.
-
- The tracking of changed pages is accomplished using the page fault
- mechanism. When we reach a point at which we want to start tracking
- changes, most pages are marked read-only and also flagged as being
- read-only because of this support. Since this cannot happen for every page
- of RAM, some are marked as untracked and always treated as modified whn
- preparing an incremental iamge. When a process attempts to modify a page
- that is marked read-only in this way, a page fault occurs, with TuxOnIce
- code marking the page writable and dirty before allowing the write to
- continue. In this way, the effect of incremental images on performance is
- minimised - a page only causes a fault once. Small modifications to the
- page allocator further reduce the number of faults that occur - free pages
- are not tracked; they are made writable and marked as dirty as part of
- being allocated.
-
- 2) Saving the incremental image / atomicity.
-
- The page fault mechanism is also used to improve the means by which
- atomicity of the image is acheived. When it is time to do an atomic copy,
- the flags for pages are reset, with the result being that it is no longer
- necessary for us to do an atomic of pageset1. Instead, we normally write
- the uncopied pages to disk. When an attempt is made to modify a page that
- has not yet been saved, the page-fault mechanism makes a copy of the page
- prior to allowing the write. This copy is then written to disk. Likewise,
- on resume, if a process attempts to write to a page that has been read
- while the rest of the image is still being loaded, a copy of that page is
- made prior to the write being allowed. At the end of loading the image,
- modified pages can thus be restored to their 'atomic copy' contents prior
- to restarting normal operation. We also mark pages that are yet to be read
- as invalid PFNs, so that we can capture as a bug any attempt by a
- half-restored kernel to access a page that hasn't yet been reloaded.
-
- f. Power down.
-
- Powering down uses standard kernel routines. TuxOnIce supports powering down
- using the ACPI S3, S4 and S5 methods or the kernel's non-ACPI power-off.
- Supporting suspend to ram (S3) as a power off option might sound strange,
- but it allows the user to quickly get their system up and running again if
- the battery doesn't run out (we just need to re-read the overwritten pages)
- and if the battery does run out (or the user removes power), they can still
- resume.
-
-4. Data Structures.
-
- TuxOnIce uses three main structures to store its metadata and configuration
- information:
-
- a) Pageflags bitmaps.
-
- TuxOnIce records which pages will be in pageset1, pageset2, the destination
- of the atomic copy and the source of the atomically restored image using
- bitmaps. The code used is that written for swsusp, with small improvements
- to match TuxOnIce's requirements.
-
- The pageset1 bitmap is thus easily stored in the image header for use at
- resume time.
-
- As mentioned above, using bitmaps also means that the amount of memory and
- storage required for recording the above information is constant. This
- greatly simplifies the work of preparing the image. In earlier versions of
- TuxOnIce, extents were used to record which pages would be stored. In that
- case, however, eating memory could result in greater fragmentation of the
- lists of pages, which in turn required more memory to store the extents and
- more storage in the image header. These could in turn require further
- freeing of memory, and another iteration. All of this complexity is removed
- by having bitmaps.
-
- Bitmaps also make a lot of sense because TuxOnIce only ever iterates
- through the lists. There is therefore no cost to not being able to find the
- nth page in order 0 time. We only need to worry about the cost of finding
- the n+1th page, given the location of the nth page. Bitwise optimisations
- help here.
-
- b) Extents for block data.
-
- TuxOnIce supports writing the image to multiple block devices. In the case
- of swap, multiple partitions and/or files may be in use, and we happily use
- them all (with the exception of compcache pages, which we allocate but do
- not use). This use of multiple block devices is accomplished as follows:
-
- Whatever the actual source of the allocated storage, the destination of the
- image can be viewed in terms of one or more block devices, and on each
- device, a list of sectors. To simplify matters, we only use contiguous,
- PAGE_SIZE aligned sectors, like the swap code does.
-
- Since sector numbers on each bdev may well not start at 0, it makes much
- more sense to use extents here. Contiguous ranges of pages can thus be
- represented in the extents by contiguous values.
-
- Variations in block size are taken account of in transforming this data
- into the parameters for bio submission.
-
- We can thus implement a layer of abstraction wherein the core of TuxOnIce
- doesn't have to worry about which device we're currently writing to or
- where in the device we are. It simply requests that the next page in the
- pageset or header be written, leaving the details to this lower layer.
- The lower layer remembers where in the sequence of devices and blocks each
- pageset starts. The header always starts at the beginning of the allocated
- storage.
-
- So extents are:
-
- struct extent {
- unsigned long minimum, maximum;
- struct extent *next;
- }
-
- These are combined into chains of extents for a device:
-
- struct extent_chain {
- int size; /* size of the extent ie sum (max-min+1) */
- int allocs, frees;
- char *name;
- struct extent *first, *last_touched;
- };
-
- For each bdev, we need to store a little more info (simplified definition):
-
- struct toi_bdev_info {
- struct block_device *bdev;
-
- char uuid[17];
- dev_t dev_t;
- int bmap_shift;
- int blocks_per_page;
- };
-
- The uuid is the main means used to identify the device in the storage
- image. This means we can cope with the dev_t representation of a device
- changing between saving the image and restoring it, as may happen on some
- bioses or in the LVM case.
-
- bmap_shift and blocks_per_page apply the effects of variations in blocks
- per page settings for the filesystem and underlying bdev. For most
- filesystems, these are the same, but for xfs, they can have independant
- values.
-
- Combining these two structures together, we have everything we need to
- record what devices and what blocks on each device are being used to
- store the image, and to submit i/o using bio_submit.
-
- The last elements in the picture are a means of recording how the storage
- is being used.
-
- We do this first and foremost by implementing a layer of abstraction on
- top of the devices and extent chains which allows us to view however many
- devices there might be as one long storage tape, with a single 'head' that
- tracks a 'current position' on the tape:
-
- struct extent_iterate_state {
- struct extent_chain *chains;
- int num_chains;
- int current_chain;
- struct extent *current_extent;
- unsigned long current_offset;
- };
-
- That is, *chains points to an array of size num_chains of extent chains.
- For the filewriter, this is always a single chain. For the swapwriter, the
- array is of size MAX_SWAPFILES.
-
- current_chain, current_extent and current_offset thus point to the current
- index in the chains array (and into a matching array of struct
- suspend_bdev_info), the current extent in that chain (to optimise access),
- and the current value in the offset.
-
- The image is divided into three parts:
- - The header
- - Pageset 1
- - Pageset 2
-
- The header always starts at the first device and first block. We know its
- size before we begin to save the image because we carefully account for
- everything that will be stored in it.
-
- The second pageset (LRU) is stored first. It begins on the next page after
- the end of the header.
-
- The first pageset is stored second. It's start location is only known once
- pageset2 has been saved, since pageset2 may be compressed as it is written.
- This location is thus recorded at the end of saving pageset2. It is page
- aligned also.
-
- Since this information is needed at resume time, and the location of extents
- in memory will differ at resume time, this needs to be stored in a portable
- way:
-
- struct extent_iterate_saved_state {
- int chain_num;
- int extent_num;
- unsigned long offset;
- };
-
- We can thus implement a layer of abstraction wherein the core of TuxOnIce
- doesn't have to worry about which device we're currently writing to or
- where in the device we are. It simply requests that the next page in the
- pageset or header be written, leaving the details to this layer, and
- invokes the routines to remember and restore the position, without having
- to worry about the details of how the data is arranged on disk or such like.
-
- c) Modules
-
- One aim in designing TuxOnIce was to make it flexible. We wanted to allow
- for the implementation of different methods of transforming a page to be
- written to disk and different methods of getting the pages stored.
-
- In early versions (the betas and perhaps Suspend1), compression support was
- inlined in the image writing code, and the data structures and code for
- managing swap were intertwined with the rest of the code. A number of people
- had expressed interest in implementing image encryption, and alternative
- methods of storing the image.
-
- In order to achieve this, TuxOnIce was given a modular design.
-
- A module is a single file which encapsulates the functionality needed
- to transform a pageset of data (encryption or compression, for example),
- or to write the pageset to a device. The former type of module is called
- a 'page-transformer', the later a 'writer'.
-
- Modules are linked together in pipeline fashion. There may be zero or more
- page transformers in a pipeline, and there is always exactly one writer.
- The pipeline follows this pattern:
-
- ---------------------------------
- | TuxOnIce Core |
- ---------------------------------
- |
- |
- ---------------------------------
- | Page transformer 1 |
- ---------------------------------
- |
- |
- ---------------------------------
- | Page transformer 2 |
- ---------------------------------
- |
- |
- ---------------------------------
- | Writer |
- ---------------------------------
-
- During the writing of an image, the core code feeds pages one at a time
- to the first module. This module performs whatever transformations it
- implements on the incoming data, completely consuming the incoming data and
- feeding output in a similar manner to the next module.
-
- All routines are SMP safe, and the final result of the transformations is
- written with an index (provided by the core) and size of the output by the
- writer. As a result, we can have multithreaded I/O without needing to
- worry about the sequence in which pages are written (or read).
-
- During reading, the pipeline works in the reverse direction. The core code
- calls the first module with the address of a buffer which should be filled.
- (Note that the buffer size is always PAGE_SIZE at this time). This module
- will in turn request data from the next module and so on down until the
- writer is made to read from the stored image.
-
- Part of definition of the structure of a module thus looks like this:
-
- int (*rw_init) (int rw, int stream_number);
- int (*rw_cleanup) (int rw);
- int (*write_chunk) (struct page *buffer_page);
- int (*read_chunk) (struct page *buffer_page, int sync);
-
- It should be noted that the _cleanup routine may be called before the
- full stream of data has been read or written. While writing the image,
- the user may (depending upon settings) choose to abort suspending, and
- if we are in the midst of writing the last portion of the image, a portion
- of the second pageset may be reread. This may also happen if an error
- occurs and we seek to abort the process of writing the image.
-
- The modular design is also useful in a number of other ways. It provides
- a means where by we can add support for:
-
- - providing overall initialisation and cleanup routines;
- - serialising configuration information in the image header;
- - providing debugging information to the user;
- - determining memory and image storage requirements;
- - dis/enabling components at run-time;
- - configuring the module (see below);
-
- ...and routines for writers specific to their work:
- - Parsing a resume= location;
- - Determining whether an image exists;
- - Marking a resume as having been attempted;
- - Invalidating an image;
-
- Since some parts of the core - the user interface and storage manager
- support - have use for some of these functions, they are registered as
- 'miscellaneous' modules as well.
-
- d) Sysfs data structures.
-
- This brings us naturally to support for configuring TuxOnIce. We desired to
- provide a way to make TuxOnIce as flexible and configurable as possible.
- The user shouldn't have to reboot just because they want to now hibernate to
- a file instead of a partition, for example.
-
- To accomplish this, TuxOnIce implements a very generic means whereby the
- core and modules can register new sysfs entries. All TuxOnIce entries use
- a single _store and _show routine, both of which are found in
- tuxonice_sysfs.c in the kernel/power directory. These routines handle the
- most common operations - getting and setting the values of bits, integers,
- longs, unsigned longs and strings in one place, and allow overrides for
- customised get and set options as well as side-effect routines for all
- reads and writes.
-
- When combined with some simple macros, a new sysfs entry can then be defined
- in just a couple of lines:
-
- SYSFS_INT("progress_granularity", SYSFS_RW, &progress_granularity, 1,
- 2048, 0, NULL),
-
- This defines a sysfs entry named "progress_granularity" which is rw and
- allows the user to access an integer stored at &progress_granularity, giving
- it a value between 1 and 2048 inclusive.
-
- Sysfs entries are registered under /sys/power/tuxonice, and entries for
- modules are located in a subdirectory named after the module.
-
diff --git a/Documentation/power/tuxonice.txt b/Documentation/power/tuxonice.txt
deleted file mode 100644
index 3bf0575ef..000000000
--- a/Documentation/power/tuxonice.txt
+++ /dev/null
@@ -1,948 +0,0 @@
- --- 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.