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authorKyungsik Lee <kyungsik.lee@lge.com>2013-07-08 16:01:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-09 10:33:30 -0700
commitcffb78b0e0b3a30b059b27a1d97500cf6464efa9 (patch)
treee20e06f58e90d3a6f3c3ff91547a9e9d51a8f230 /include/linux/lz4.h
parent4df87bb7b6a22dfc6fdd5abb3dd362b3af2c164d (diff)
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decompressor: add LZ4 decompressor module
Add support for LZ4 decompression in the Linux Kernel. LZ4 Decompression APIs for kernel are based on LZ4 implementation by Yann Collet. Benchmark Results(PATCH v3) 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 20.1MB/s, 25.2MB/s(UA) 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, 52.2MB/s(UA) LZ4 6.5MB 86.7MB/s - UA: Unaligned memory Access support - Latest patch set for LZO applied This patch set is for adding support for LZ4-compressed Kernel. LZ4 is a very fast lossless compression algorithm and it also features an extremely fast decoder [1]. But we have five of decompressors already and one question which does arise, however, is that of where do we stop adding new ones? This issue had been discussed and came to the conclusion [2]. Russell King said that we should have: - one decompressor which is the fastest - one decompressor for the highest compression ratio - one popular decompressor (eg conventional gzip) If we have a replacement one for one of these, then it should do exactly that: replace it. The benchmark shows that an 8% increase in image size vs a 66% increase in decompression speed compared to LZO(which has been known as the fastest decompressor in the Kernel). Therefore the "fast but may not be small" compression title has clearly been taken by LZ4 [3]. [1] http://code.google.com/p/lz4/ [2] http://thread.gmane.org/gmane.linux.kbuild.devel/9157 [3] http://thread.gmane.org/gmane.linux.kbuild.devel/9347 LZ4 homepage: http://fastcompression.blogspot.com/p/lz4.html LZ4 source repository: http://code.google.com/p/lz4/ Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com> Signed-off-by: Yann Collet <yann.collet.73@gmail.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Borislav Petkov <bp@alien8.de> Cc: Florian Fainelli <florian@openwrt.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/lz4.h')
-rw-r--r--include/linux/lz4.h51
1 files changed, 51 insertions, 0 deletions
diff --git a/include/linux/lz4.h b/include/linux/lz4.h
new file mode 100644
index 000000000000..7f6c75a093f8
--- /dev/null
+++ b/include/linux/lz4.h
@@ -0,0 +1,51 @@
+#ifndef __LZ4_H__
+#define __LZ4_H__
+/*
+ * LZ4 Kernel Interface
+ *
+ * Copyright (C) 2013, LG Electronics, Kyungsik Lee <kyungsik.lee@lge.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/*
+ * lz4_compressbound()
+ * Provides the maximum size that LZ4 may output in a "worst case" scenario
+ * (input data not compressible)
+ */
+static inline size_t lz4_compressbound(size_t isize)
+{
+ return isize + (isize / 255) + 16;
+}
+
+/*
+ * lz4_decompress()
+ * src : source address of the compressed data
+ * src_len : is the input size, whcih is returned after decompress done
+ * dest : output buffer address of the decompressed data
+ * actual_dest_len: is the size of uncompressed data, supposing it's known
+ * return : Success if return 0
+ * Error if return (< 0)
+ * note : Destination buffer must be already allocated.
+ * slightly faster than lz4_decompress_unknownoutputsize()
+ */
+int lz4_decompress(const char *src, size_t *src_len, char *dest,
+ size_t actual_dest_len);
+
+/*
+ * lz4_decompress_unknownoutputsize()
+ * src : source address of the compressed data
+ * src_len : is the input size, therefore the compressed size
+ * dest : output buffer address of the decompressed data
+ * dest_len: is the max size of the destination buffer, which is
+ * returned with actual size of decompressed data after
+ * decompress done
+ * return : Success if return 0
+ * Error if return (< 0)
+ * note : Destination buffer must be already allocated.
+ */
+int lz4_decompress_unknownoutputsize(const char *src, size_t src_len,
+ char *dest, size_t *dest_len);
+#endif