Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269395AbUIIJnU (ORCPT ); Thu, 9 Sep 2004 05:43:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269399AbUIIJnU (ORCPT ); Thu, 9 Sep 2004 05:43:20 -0400 Received: from [213.146.154.40] ([213.146.154.40]:35500 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S269398AbUIIJnD (ORCPT ); Thu, 9 Sep 2004 05:43:03 -0400 Subject: Re: What File System supports Application XIP From: David Woodhouse To: Paulo Marques Cc: colin , linux-kernel@vger.kernel.org In-Reply-To: <4140200B.9060408@grupopie.com> References: <009901c4964a$be2468e0$8b1a13ac@realtek.com.tw> <4140200B.9060408@grupopie.com> Content-Type: text/plain Message-Id: <1094722976.4083.1550.camel@hades.cambridge.redhat.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2.dwmw2.1) Date: Thu, 09 Sep 2004 10:42:57 +0100 Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1584 Lines: 39 On Thu, 2004-09-09 at 10:19 +0100, Paulo Marques wrote: > colin wrote: > > > > Hi there, > > We are developing embedded Linux system. Performance is our consideration. > > We hope some applications can run as fast as possible, > > and are think if they can be put in a filesystem image, which resides in > > RAM, and run in XIP (eXecute In Place) manners. > > I know that Cramfs has supported Application XIP. Is there any other FS that > > also supports it? Ramdisk? Ramfs? Romfs? > > Obvisously cramfs can not support XIP, because the "in-place" image > is compressed (unless you have a processor that can execute compressed > code :) Actually there are hacks floating around which do let you use XIP with cramfs -- obviously you have to dispense with compression for the files you want to access that way. You won't gain at runtime by using XIP though. Your code and data will end up in RAM _whatever_ file system you use, and you'll be running from page cache. You may get a _slightly_ faster startup time after reboot if you use XIP from flash, because it doesn't have to be loaded into RAM first. But that comes at the cost of making it all a low slower during normal operation -- it's a lot slower to fetch icache lines from flash than it is from RAM. Arjan's right -- you almost certainly don't really want XIP. -- dwmw2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/