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Date:   Fri, 13 Oct 2023 07:12:10 +0530
From:   Nikhil V <quic_nprakash@...cinc.com>
To:     Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Tejun Heo <tj@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <quic_pkondeti@...cinc.com>,
        <quic_kprasan@...cinc.com>, <quic_mpilaniy@...cinc.com>,
        <quic_shrekk@...cinc.com>, <mpleshivenkov@...gle.com>,
        <ericyin@...gle.com>
Subject: Re: [PATCH 0/4] PM: hibernate: LZ4 compression support



On 10/4/2023 3:00 PM, 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                      |  85 +++++++-
>   kernel/power/power.h                          |  19 ++
>   kernel/power/swap.c                           | 189 +++++++++++-------
>   5 files changed, 250 insertions(+), 74 deletions(-)
> 

Hi @Rafael/@...el/@Len,

Could you please let me know if you have any concerns/comments on this 
approach?

Regards,
Nikhil V

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