[PATCH v3 0/4] PM: hibernate: LZ4 compression support

[Nikhil V]

This patch series covers the following:
1. Renaming lzo* to generic names, except for lzo_xxx() APIs. This is
used in the next patch where we move to crypto based APIs for
compression. There are no functional changes introduced by this
approach.


2. Replace LZO library calls with crypto generic APIs

Currently for hibernation, LZO is the only compression algorithm
available and uses the existing LZO library calls. However, there
is no flexibility to switch to other algorithms which provides better
results. The main idea is that different compression algorithms have
different characteristics and hibernation may benefit when it uses
alternate algorithms.

By moving to crypto based APIs, it lays a foundation to use other
compression algorithms for hibernation.


3. LZ4 compression

Extend the support for LZ4 compression to be used with hibernation.
The main idea is that different compression algorithms have different
characteristics and hibernation may benefit when it uses any of these
algorithms: a default algorithm, having higher compression rate but is
slower(compression/decompression) and a secondary algorithm, that is
faster(compression/decompression) but has lower compression rate.

LZ4 algorithm has better decompression speeds over LZO. This reduces
the hibernation image restore time.
As per test results:
                                    LZO             LZ4
Size before Compression(bytes)   682696704       682393600
Size after Compression(bytes)    146502402       155993547
Decompression Rate               335.02 MB/s     501.05 MB/s
Restore time                       4.4s             3.8s

LZO is the default compression algorithm used for hibernation. Enable
CONFIG_HIBERNATION_DEF_COMP_LZ4 to set the default compressor as LZ4.

Compression Benchmarks: https://github.com/lz4/lz4


4. Support to select compression algorithm

Currently the default compression algorithm is selected based on
Kconfig. Introduce a kernel command line parameter "hib_compression" to
override this behaviour.

Users can set "hib_compression" command line parameter to specify
the algorithm.
Usage:
    LZO: hib_compression=lzo
    LZ4: hib_compression=lz4
LZO is the default compression algorithm used with hibernation.


Changes in v3:
 - Rebased to v6.8-rc1 after resolving the minor conflicts.
 - Link to v2:
 https://lore.kernel.org/all/cover.1700048610.git.quic_nprakash@xxxxxxxxxxx/

Changes in v2:
 - Fixed build issues reported by kernel test robot for ARCH=sh, [1].
 [1] https://lore.kernel.org/oe-kbuild-all/202310171226.pLUPeuC7-lkp@xxxxxxxxx/
 - Link to v1:
 https://lore.kernel.org/all/cover.1696410298.git.quic_nprakash@xxxxxxxxxxx/

Nikhil V (4):
  PM: hibernate: Rename lzo* to make it generic
  PM: hibernate: Move to crypto APIs for LZO compression
  PM: hibernate: Add support for LZ4 compression for hibernation
  PM: hibernate: Support to select compression algorithm

 .../admin-guide/kernel-parameters.txt         |   6 +
 kernel/power/Kconfig                          |  26 ++-
 kernel/power/hibernate.c                      |  85 +++++++-
 kernel/power/power.h                          |  19 ++
 kernel/power/swap.c                           | 189 +++++++++++-------
 5 files changed, 251 insertions(+), 74 deletions(-)


base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
-- 
2.17.1