[RFC PATCH v2 0/4] Add support for LZ4-compressed kernel

[Markus F.X.J. Oberhumer]

On 2013-02-26 07:24, Kyungsik Lee wrote:
> Hi,
> 
> [...]
> 
> Through the benchmark, it was found that -Os Compiler flag for
> decompress.o brought better decompression performance in most of cases
> (ex, different compiler and hardware spec.) in ARM architecture.
> 
> Lastly, CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not always the best
> option even though it is supported. The decompression speed can be
> slightly slower in some cases.
> 
> This patchset is based on 3.8.
> 
> Any comments are appreciated.

Did you actually *try* the new LZO version and the patch (which is attached
once again) as explained in https://lkml.org/lkml/2013/2/3/367 ?

Because the new LZO version is faster than LZ4 in my testing, at least
when comparing apples with apples and enabling unaligned access in
BOTH versions:

armv7 (Cortex-A9), Linaro gcc-4.6 -O3, Silesia test corpus, 256 kB block-size:

                   compression speed   decompression speed

  LZO-2012    :          44 MB/sec          117 MB/sec     no unaligned access
  LZO-2013-UA :          47 MB/sec          167 MB/sec     Unaligned Access
  LZ4 r88  UA :          46 MB/sec          154 MB/sec     Unaligned Access

~Markus


> 
> Thanks,
> Kyungsik
> 
> 
> Benchmark Results(PATCH v2)
> Compiler: Linaro ARM gcc 4.6.2
> 1. ARMv7, 1.5GHz based board
>    Kernel: linux 3.4
>    Uncompressed Kernel Size: 14MB
>         Compressed Size  Decompression Speed
>    LZO  6.7MB            21.1MB/s
>    LZ4  7.3MB            29.1MB/s, 45.6MB/s(UA)
> 2. ARMv7, 1.7GHz based board
>    Kernel: linux 3.7
>    Uncompressed Kernel Size: 14MB
>         Compressed Size  Decompression Speed
>    LZO  6.0MB            34.1MB/s
>    LZ4  6.5MB            86.7MB/s
> UA: Unaligned memory Access support
> 
> 
> Change log: v2
> - Clean up code
> - Enable unaligned access for ARM v6 and above with
>   CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> - Add lz4_decompress() for faster decompression with
>   uncompressed output size
> - Use lz4_decompress() for LZ4-compressed kernel during
>   boot-process
> - Apply -Os to decompress.o to improve decompress
>   performance during boot-up process
> 
> 
> Kyungsik Lee (4):
>   decompressor: Add LZ4 decompressor module
>   lib: Add support for LZ4-compressed kernel
>   arm: Add support for LZ4-compressed kernel
>   x86: Add support for LZ4-compressed kernel
> 
>  arch/arm/Kconfig                      |   1 +
>  arch/arm/boot/compressed/.gitignore   |   1 +
>  arch/arm/boot/compressed/Makefile     |   6 +-
>  arch/arm/boot/compressed/decompress.c |   4 +
>  arch/arm/boot/compressed/piggy.lz4.S  |   6 +
>  arch/x86/Kconfig                      |   1 +
>  arch/x86/boot/compressed/Makefile     |   5 +-
>  arch/x86/boot/compressed/misc.c       |   4 +
>  include/linux/decompress/unlz4.h      |  10 +
>  include/linux/lz4.h                   |  48 +++++
>  init/Kconfig                          |  13 +-
>  lib/Kconfig                           |   7 +
>  lib/Makefile                          |   2 +
>  lib/decompress.c                      |   5 +
>  lib/decompress_unlz4.c                | 190 +++++++++++++++++++
>  lib/lz4/Makefile                      |   1 +
>  lib/lz4/lz4_decompress.c              | 331 ++++++++++++++++++++++++++++++++++
>  lib/lz4/lz4defs.h                     |  93 ++++++++++
>  scripts/Makefile.lib                  |   5 +
>  usr/Kconfig                           |   9 +
>  20 files changed, 739 insertions(+), 3 deletions(-)
>  create mode 100644 arch/arm/boot/compressed/piggy.lz4.S
>  create mode 100644 include/linux/decompress/unlz4.h
>  create mode 100644 include/linux/lz4.h
>  create mode 100644 lib/decompress_unlz4.c
>  create mode 100644 lib/lz4/Makefile
>  create mode 100644 lib/lz4/lz4_decompress.c
>  create mode 100644 lib/lz4/lz4defs.h
> 


-- 
Markus Oberhumer, <markus at oberhumer.com>, http://www.oberhumer.com/
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