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

[Pavan Kondeti]

On Tue, Sep 26, 2023 at 02:27:10PM +0530, Nikhil V wrote:
> 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.
> 
> 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                          |  25 ++-
>  kernel/power/hibernate.c                      |  83 +++++++-
>  kernel/power/power.h                          |  19 ++
>  kernel/power/swap.c                           | 189 +++++++++++-------
>  5 files changed, 248 insertions(+), 74 deletions(-)
> 

I have tested this series on x86 QEMU with v6.6-rc3 (plus another patch
from pm-next tree i.e "PM: hibernate: use __get_safe_page() rather than
touching the list"). It works as advertised.

Thanks,
Pavan