From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42838 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754532Ab3A1WZN (ORCPT ); Mon, 28 Jan 2013 17:25:13 -0500 Date: Mon, 28 Jan 2013 14:25:10 -0800 From: Andrew Morton Subject: Re: [RFC PATCH 0/4] Add support for LZ4-compressed kernels Message-Id: <20130128142510.68092e10.akpm@linux-foundation.org> In-Reply-To: <1359179447-31118-1-git-send-email-kyungsik.lee@lge.com> References: <1359179447-31118-1-git-send-email-kyungsik.lee@lge.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Kyungsik Lee Cc: Russell King , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, x86@kernel.org, Nitin Gupta , Richard Purdie , Josh Triplett , Joe Millenbach , Albin Tonnerre , hyojun.im@lge.com, chan.jeong@lge.com, gunho.lee@lge.com, minchan.kim@lge.com, namhyung.kim@lge.com, raphael.andy.lee@gmail.com, CE Linux Developers List 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?