linux-kernel - Re: [PATCH RESEND v2 0/4] PM: hibernate: LZ4 compression support

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Date:   Wed, 29 Nov 2023 15:49:34 +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>,
        Randy Dunlap <rdunlap@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Tejun Heo <tj@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        <linux-pm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...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 RESEND v2 0/4] PM: hibernate: LZ4 compression support



On 11/15/2023 5:52 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.
> 
> 
> 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@intel.com/
> 
> 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: b85ea95d086471afb4ad062012a4d73cd328fa86

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

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

FYI: We have tested this on QEMU and its working fine.

Logs(suspend):
[   75.242227] PM: Using 3 thread(s) for lz4 compression
[   75.243043] PM: Compressing and saving image data (17495 pages)...
[   75.243917] PM: Image saving progress:   0%
[   75.261727] PM: Image saving progress:  10%
[   75.277968] PM: Image saving progress:  20%
[   75.290927] PM: Image saving progress:  30%
[   75.305186] PM: Image saving progress:  40%
[   75.318252] PM: Image saving progress:  50%
[   75.330310] PM: Image saving progress:  60%
[   75.345906] PM: Image saving progress:  70%
[   75.359054] PM: Image saving progress:  80%
[   75.372176] PM: Image saving progress:  90%
[   75.388411] PM: Image saving progress: 100%
[   75.389775] PM: Image saving done
[   75.390397] PM: hibernation: Wrote 69980 kbytes in 0.14 seconds 
(499.85 MB/s)
[   75.391591] PM: Image size after compression: 28242 kbytes
[   75.393089] PM: S|
[   75.399784] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[   75.439170] sd 0:0:0:0: [sda] Stopping disk
[   75.501461] ACPI: PM: Preparing to enter system sleep state S5
[   75.502766] reboot: Power down



Logs(resume):
[    1.063248] PM: hibernation: resume from hibernation
[    1.072868] Freezing user space processes
[    1.073707] Freezing user space processes completed (elapsed 0.000 
seconds)
[    1.075192] OOM killer disabled.
[    1.075837] Freezing remaining freezable tasks
[    1.078010] Freezing remaining freezable tasks completed (elapsed 
0.001 seconds)
[    1.087489] PM: Using 3 thread(s) for lz4 decompression
[    1.088570] PM: Loading and decompressing image data (17495 pages)...
[    1.125549] PM: Image loading progress:   0%
[    1.190380] PM: Image loading progress:  10%
[    1.204963] PM: Image loading progress:  20%
[    1.218988] PM: Image loading progress:  30%
[    1.233697] PM: Image loading progress:  40%
[    1.248658] PM: Image loading progress:  50%
[    1.262910] PM: Image loading progress:  60%
[    1.276966] PM: Image loading progress:  70%
[    1.290517] PM: Image loading progress:  80%
[    1.305427] PM: Image loading progress:  90%
[    1.320666] PM: Image loading progress: 100%
[    1.321866] PM: Image loading done
[    1.322599] PM: hibernation: Read 69980 kbytes in 0.23 seconds 
(304.26 MB/s)
[    1.324795] printk: Suspending console(s) (use no_console_suspend to 
debug)
[   74.943801] ata1.00: Entering standby power mode


Thanks,
Nikhil V