From mboxrd@z Thu Jan 1 00:00:00 1970 From: kyungsik.lee@lge.com (kyungsik.lee) Date: Fri, 01 Feb 2013 16:00:57 +0900 Subject: [RFC PATCH 0/4] Add support for LZ4-compressed kernels In-Reply-To: <254788880.18003.1359493798737.JavaMail.tomcat@be12> References: <1359179447-31118-1-git-send-email-kyungsik.lee@lge.com>, <20130128142510.68092e10.akpm@linux-foundation.org> <254788880.18003.1359493798737.JavaMail.tomcat@be12> Message-ID: <510B6829.7050908@lge.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2013-01-30 ?? 6:09, Rajesh Pawar wrote: >> Andrew Morton wrote: >> >> On Sat, 26 Jan 2013 14:50:43 +0900 >> Kyungsik Lee wrote: >>> This patchset is for supporting LZ4 compressed kernel and initial ramdisk on >>> the x86 and ARM architectures. >>> >>> According to [[http://code.google.com/p/lz4/,]] LZ4 is a very fast lossless >>> compression algorithm and also features an extremely fast decoder. >>> >>> Kernel Decompression APIs are based on implementation by Yann Collet >>> ([[http://code.google.com/p/lz4/source/checkout]]). >>> De/compression Tools are also provided from the site above. >>> >>> The initial test result on ARM(v7) based board shows that the size of kernel >>> with LZ4 compressed is 8% bigger than LZO compressed but the decompressing >>> speed is faster(especially under the enabled unaligned memory access). >>> >>> Test: 3.4 based kernel built with many modules >>> Uncompressed kernel size: 13MB >>> lzo: 6.3MB, 301ms >>> lz4: 6.8MB, 251ms(167ms, with enabled unaligned memory access) >>> >>> It seems that it___s worth trying LZ4 compressed kernel image or ramdisk >>> for making the kernel boot more faster. >>> >>> ... >>> >>> 20 files changed, 663 insertions(+), 3 deletions(-) >>> >>> ... >>> >> What's this "with enabled unaligned memory access" thing? You mean "if >> the arch supports CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS"? If so, >> that's only x86, which isn't really in the target market for this >> patch, yes? >> It's a lot of code for a 50ms boot-time improvement. Does anyone have >> any opinions on whether or not the benefits are worth the cost? > BTW, what happened to the proposed LZO update - woudn't it better to merge this first? > > Also, under the hood LZ4 seems to be quite similar to LZO, so probably > LZO speed would also greatly benefit from unaligned access and some other > ARM optimisations > I didn't test with the proposed LZO update you mentioned. Sorry, which one do you mean? I did some tests with the latest LZO in the mainline. As a result, LZO is not faster in an unaligned access enabled on ARM. Actually Slower. Decompression time: 336ms(383ms, with unaligned access enabled) You may refer to https://lkml.org/lkml/2012/10/7/85 to know more about it. Thanks, Kyungsik Thanks, Kyungsik