From 7dd65feb6c603e13eba501c34c662259ab38e70e Mon Sep 17 00:00:00 2001 From: Albin Tonnerre Date: Fri, 8 Jan 2010 14:42:42 -0800 Subject: lib: add support for LZO-compressed kernels This patch series adds generic support for creating and extracting LZO-compressed kernel images, as well as support for using such images on the x86 and ARM architectures, and support for creating and using LZO-compressed initrd and initramfs images. Russell King said: : Testing on a Cortex A9 model: : - lzo decompressor is 65% of the time gzip takes to decompress a kernel : - lzo kernel is 9% larger than a gzip kernel : : which I'm happy to say confirms your figures when comparing the two. : : However, when comparing your new gzip code to the old gzip code: : - new is 99% of the size of the old code : - new takes 42% of the time to decompress than the old code : : What this means is that for a proper comparison, the results get even better: : - lzo is 7.5% larger than the old gzip'd kernel image : - lzo takes 28% of the time that the old gzip code took : : So the expense seems definitely worth the effort. The only reason I : can think of ever using gzip would be if you needed the additional : compression (eg, because you have limited flash to store the image.) : : I would argue that the default for ARM should therefore be LZO. This patch: The lzo compressor is worse than gzip at compression, but faster at extraction. Here are some figures for an ARM board I'm working on: Uncompressed size: 3.24Mo gzip 1.61Mo 0.72s lzo 1.75Mo 0.48s So for a compression ratio that is still relatively close to gzip, it's much faster to extract, at least in that case. This part contains: - Makefile routine to support lzo compression - Fixes to the existing lzo compressor so that it can be used in compressed kernels - wrapper around the existing lzo1x_decompress, as it only extracts one block at a time, while we need to extract a whole file here - config dialog for kernel compression [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: cleanup] Signed-off-by: Albin Tonnerre Tested-by: Wu Zhangjin Acked-by: "H. Peter Anvin" Cc: Ingo Molnar Cc: Thomas Gleixner Tested-by: Russell King Acked-by: Russell King Cc: Ralf Baechle Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/Kconfig | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index a23da9f0180..d95ca7cd5d4 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -115,10 +115,13 @@ config HAVE_KERNEL_BZIP2 config HAVE_KERNEL_LZMA bool +config HAVE_KERNEL_LZO + bool + choice prompt "Kernel compression mode" default KERNEL_GZIP - depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA + depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO help The linux kernel is a kind of self-extracting executable. Several compression algorithms are available, which differ @@ -141,9 +144,8 @@ config KERNEL_GZIP bool "Gzip" depends on HAVE_KERNEL_GZIP help - The old and tried gzip compression. Its compression ratio is - the poorest among the 3 choices; however its speed (both - compression and decompression) is the fastest. + The old and tried gzip compression. It provides a good balance + between compression ratio and decompression speed. config KERNEL_BZIP2 bool "Bzip2" @@ -164,6 +166,14 @@ config KERNEL_LZMA two. Compression is slowest. The kernel size is about 33% smaller with LZMA in comparison to gzip. +config KERNEL_LZO + bool "LZO" + depends on HAVE_KERNEL_LZO + help + Its compression ratio is the poorest among the 4. The kernel + size is about about 10% bigger than gzip; however its speed + (both compression and decompression) is the fastest. + endchoice config SWAP -- cgit v1.2.3-18-g5258