From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Xin Zhao" Subject: Linux page cache issue? Date: Wed, 28 Mar 2007 02:45:23 -0400 Message-ID: <4ae3c140703272345y3b3cb3cexf4c4b63e0035d5b9@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: linux-kernel , linux-fsdevel , "Xin Zhao" Return-path: Received: from wr-out-0506.google.com ([64.233.184.232]:41306 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753176AbXC1GpZ (ORCPT ); Wed, 28 Mar 2007 02:45:25 -0400 Received: by wr-out-0506.google.com with SMTP id 76so2268286wra for ; Tue, 27 Mar 2007 23:45:24 -0700 (PDT) Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.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