From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: Linux page cache issue? Date: Mon, 2 Apr 2007 14:51:24 +0200 Message-ID: <20070402125124.GI3728@duck.suse.cz> References: <4ae3c140703272345y3b3cb3cexf4c4b63e0035d5b9@mail.gmail.com> <1175091028.12882.15.camel@kleikamp.austin.ibm.com> <4ae3c140703280839q72164accic94666d7801243c1@mail.gmail.com> <20070329092745.GA14616@atrey.karlin.mff.cuni.cz> <4ae3c140703290741p58199472u3bf9f3f58e4d1db1@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dave Kleikamp , linux-kernel , linux-fsdevel To: Xin Zhao Return-path: Received: from styx.suse.cz ([82.119.242.94]:34450 "EHLO duck.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933979AbXDBMoN (ORCPT ); Mon, 2 Apr 2007 08:44:13 -0400 Content-Disposition: inline In-Reply-To: <4ae3c140703290741p58199472u3bf9f3f58e4d1db1@mail.gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi Xin, On Thu 29-03-07 10:41:01, Xin Zhao wrote: > I know we can use device inode's radix tree to achieve the same goal. > The only downside could be: First, by default, Linux will not add the > data pages into that radix tree. Only when a file is opened in Right. > O_DIRECT, the data pages will be put into dev's radix tree. Moreover, If you use O_DIRECT, I don't think the data will and in any radix tree - ideally they go directly to disk in this case. > if the partition is big, I am not sure whether the lookup overhead is > an issue. So it might need some optimization. Maybe, but I'd not say so as my first guess. > Can you elaborate more about the aliasing issues mentioned in your > email? I do have some mechanisms to handle the following situation: > suppose two files share same data blocks. Now two processes open the > two files separately. If one process writes a file, the other file > will be affected. Is this the aliasing issue you referred to? Yes, this is exactly what I meant. Note that these problems are not only about writes but also about truncate and such... Honza -- Jan Kara SuSE CR Labs