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

[Rafael J. Wysocki]

On Mon, Jan 22, 2024 at 1:14 PM Nikhil V <quic_nprakash@xxxxxxxxxxx> wrote:
>
>
>
> On 12/12/2023 6:14 PM, Rafael J. Wysocki wrote:
> > Hi,
> >
> > On Wed, Nov 29, 2023 at 11:20 AM Nikhil V <quic_nprakash@xxxxxxxxxxx> wrote:
> >>
> >>
> >> 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@xxxxxxxxx/
> >>>
> >>> 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/@Pavel/@Len,
> >>
> >> Could you please let me know if you have any concerns on this approach?
> >
> > Not really a concern, but that is a significant change that I would
> > rather make early in the cycle, which means after the 6.8 merge
> > window.
> >
> > No need to resend unless there is something to address in which case
> > I'll let you know.
> >
> > Thanks!
> >
> >> 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
>
>
> Hi @Rafael
>
> We have picked this patch series on 6.8-rc1 and tested the functionality
> on QEMU. Its working fine. However, while applying the patches we could
> see minor conflicts. Could you please let me know if we need to push a
> new version after resolving these conflicts?

It will help.

I can resolve the conflicts, but I may make mistakes in the process.

Thanks!