From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262950AbTJJQEM (ORCPT ); Fri, 10 Oct 2003 12:04:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262948AbTJJQCr (ORCPT ); Fri, 10 Oct 2003 12:02:47 -0400 Received: from mail.jlokier.co.uk ([81.29.64.88]:55691 "EHLO mail.shareable.org") by vger.kernel.org with ESMTP id S262817AbTJJQCB (ORCPT ); Fri, 10 Oct 2003 12:02:01 -0400 Date: Fri, 10 Oct 2003 17:01:44 +0100 From: Jamie Lokier To: Linus Torvalds , Trond Myklebust , Ulrich Drepper , Linux Kernel Subject: Re: statfs() / statvfs() syscall ballsup... Message-ID: <20031010160144.GI28795@mail.shareable.org> References: <20031010122755.GC22908@ca-server1.us.oracle.com> <20031010152710.GA28773@ca-server1.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031010152710.GA28773@ca-server1.us.oracle.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Joel Becker wrote: > Where I work doesn't change the need for O_DIRECT. If your Big > App has it's own cache, why copy the cache in the kernel? That just > wastes RAM. Why don't you _share_ the App's cache with the kernel's? That's what mmap() and remap_file_pages() are for. > If your app is sharing data, whether physical disk, logical > disk, or via some network filesystem or storage device, you must > absolutely guarantee that reads and writes hit the storage, not the > kernel cache which has no idea whether another node wrote an update or > needs a cache flush. That's tough to guarantee at the platter level regardless of O_DIRECT, but otherwise: you have fdatasync() and msync(). > If Linux came up with a better, cleaner method, Oracle might change. Take a look at remap_file_pages() and write a note here to say if it fits the bill. I thought remap_file_pages() was added for Oracle, but perhaps it was for a more modern database ;) Thanks, -- Jamie