From mboxrd@z Thu Jan 1 00:00:00 1970 From: markus@oberhumer.com (Markus F.X.J. Oberhumer) Date: Mon, 04 Feb 2013 02:37:08 +0100 Subject: [RFC PATCH 0/4] Add support for LZ4-compressed kernels In-Reply-To: <510B6829.7050908@lge.com> References: <1359179447-31118-1-git-send-email-kyungsik.lee@lge.com>, <20130128142510.68092e10.akpm@linux-foundation.org> <254788880.18003.1359493798737.JavaMail.tomcat@be12> <510B6829.7050908@lge.com> Message-ID: <510F10C4.2080903@oberhumer.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2013-02-01 08:00, kyungsik.lee wrote: > On 2013-01-30 ?? 6:09, Rajesh Pawar wrote: >>> Andrew Morton wrote: >>> >>> On Sat, 26 Jan 2013 14:50:43 +0900 >>> Kyungsik Lee wrote: >>>> [...] >>>> >>> 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. In fact you can easily improve LZO decompression speed on armv7 by almost 50% by adding just a few lines for enabling unaligend access: armv7 (Cortex-A9), Linaro gcc-4.6 -O3, Silesia test corpus, 256 kB block-size: compression speed decompression speed LZO-2005 : 27 MB/sec 84 MB/sec LZO-2012 : 44 MB/sec 117 MB/sec LZO-2013-UA : 47 MB/sec 167 MB/sec Please see my other mail to LKML for details. Cheers, Markus > 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 > -- Markus Oberhumer, , http://www.oberhumer.com/