From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932796AbXC1Gp0 (ORCPT ); Wed, 28 Mar 2007 02:45:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753094AbXC1Gp0 (ORCPT ); Wed, 28 Mar 2007 02:45:26 -0400 Received: from wr-out-0506.google.com ([64.233.184.233]:41176 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753203AbXC1GpZ (ORCPT ); Wed, 28 Mar 2007 02:45:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=mnhOqCn1iFBPZCUf5lopNFbchkyLUYmkRtuq02cxfzWpjmWOqVa69vFmDY3x70X+HhqQe3Rj+2Hp3dx8UUn+qFtPitY6PGVyyZG6dAvgloadDB2BChEScvUnkzFixtgbS74XOL1PDSe1oq3B5L7zLAlTmpuolxtareRgbnqLoMI= Message-ID: <4ae3c140703272345y3b3cb3cexf4c4b63e0035d5b9@mail.gmail.com> Date: Wed, 28 Mar 2007 02:45:23 -0400 From: "Xin Zhao" To: linux-kernel , linux-fsdevel , "Xin Zhao" Subject: Linux page cache issue? MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, If a Linux process opens and reads a file A, then it closes the file. Will Linux keep the file A's data in cache for a while in case another process opens and reads the same in a short time? I think that is what I heard before. But after I digged into the kernel code, I am confused. When a process closes the file A, iput() will be called, which in turn calls the follows two functions: iput_final()->generic_drop_inode() But from the following calling chain, we can see that file close will eventually lead to evict and free all cached pages. Actually in truncate_complete_page(), the pages will be freed. This seems to imply that Linux has to re-read the same data from disk even if another process B read the same file right after process A closes the file. That does not make sense to me. /***calling chain ***/ generic_delete_inode/generic_forget_inode()-> truncate_inode_pages()->truncate_inode_pages_range()-> truncate_complete_page()->remove_from_page_cache()-> __remove_from_page_cache()->radix_tree_delete() Am I missing something? Can someone please provide some advise? Thanks a lot -x