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

Markus F.X.J. Oberhumer
2013-02-26T20:33:43Z

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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@oberhumer.com>, http://www.oberhumer.com/

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commit 8745b927fcfcd6953ada9bd1220a73083db5948a
Author: Markus F.X.J. Oberhumer <markus@oberhumer.com>
Date: Mon Feb 4 02:26:14 2013 +0100

lib/lzo: huge LZO decompression speedup on ARM by using unaligned access

Signed-off-by: Markus F.X.J. Oberhumer <markus@oberhumer.com>

diff --git a/lib/lzo/lzo1x_decompress_safe.c b/lib/lzo/lzo1x_decompress_safe.c
index 569985d..e3edc5f 100644
--- a/lib/lzo/lzo1x_decompress_safe.c
+++ b/lib/lzo/lzo1x_decompress_safe.c
@@ -72,9 +72,11 @@ copy_literal_run:
COPY8(op, ip);
op += 8;
ip += 8;
+# if !defined(__arm__)
COPY8(op, ip);
op += 8;
ip += 8;
+# endif
} while (ip < ie);
ip = ie;
op = oe;
@@ -159,9 +161,11 @@ copy_literal_run:
COPY8(op, m_pos);
op += 8;
m_pos += 8;
+# if !defined(__arm__)
COPY8(op, m_pos);
op += 8;
m_pos += 8;
+# endif
} while (op < oe);
op = oe;
if (HAVE_IP(6)) {
diff --git a/lib/lzo/lzodefs.h b/lib/lzo/lzodefs.h
index 5a4beb2..b230601 100644
--- a/lib/lzo/lzodefs.h
+++ b/lib/lzo/lzodefs.h
@@ -12,8 +12,14 @@
*/

+#if 1 && defined(__arm__) && ((__LINUX_ARM_ARCH__ >= 6) || defined(__ARM_FEATURE_UNALIGNED))
+#define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS 1
+#define COPY4(dst, src) \
+ * (u32 *) (void *) (dst) = * (const u32 *) (const void *) (src)
+#else
#define COPY4(dst, src) \
put_unaligned(get_unaligned((const u32 *)(src)), (u32 *)(dst))
+#endif
#if defined(__x86_64__)
#define COPY8(dst, src) \
put_unaligned(get_unaligned((const u64 *)(src)), (u64 *)(dst))