Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760167Ab3HOG3E (ORCPT ); Thu, 15 Aug 2013 02:29:04 -0400 Received: from mail-vc0-f179.google.com ([209.85.220.179]:39506 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753442Ab3HOG3B (ORCPT ); Thu, 15 Aug 2013 02:29:01 -0400 MIME-Version: 1.0 In-Reply-To: References: <520BB9EF.5020308@linux.intel.com> <20130814194359.GA22316@thunk.org> <520BED7A.4000903@intel.com> <20130814230648.GD22316@thunk.org> <20130815011101.GA3572@thunk.org> <20130815021028.GM6023@dastard> <20130815060149.GP6023@dastard> From: Andy Lutomirski Date: Wed, 14 Aug 2013 23:28:40 -0700 Message-ID: Subject: Re: page fault scalability (ext3, ext4, xfs) To: David Lang Cc: Dave Chinner , "Theodore Ts'o" , Dave Hansen , Dave Hansen , Linux FS Devel , xfs@oss.sgi.com, "linux-ext4@vger.kernel.org" , Jan Kara , LKML , Tim Chen , Andi Kleen Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1571 Lines: 35 On Wed, Aug 14, 2013 at 11:18 PM, David Lang wrote: > On Wed, 14 Aug 2013, Andy Lutomirski wrote: > >>> The big problem with this approach is that not doing the >>> timestamp update on page faults is going to break the inode change >>> version counting because for ext4, btrfs and XFS it takes a >>> transaction to bump that counter. NFS needs to know the moment a >>> file is changed in memory, not when it is written to disk. Also, NFS >>> requires the change to the counter to be persistent over server >>> failures, so it needs to be changed as part of a transaction.... >> >> >> NFS can do whatever it wants, although I suspect that even NFS can get >> away with deferring cmtime updates. > > > NFS already has to do syncs to make sure the data is safe on disk, have a > flag that NFS can use to make the ctime safe, everyone else can get the > performance improvement and NFS can have it's slow-but-safe approach. > I don't see the current code that updates times for NFS. I'm not planning on making any changes that'll affect NFS at all (i.e. I don't think any flag will be needed), but I'd be more confident if I understand why it worked in the first place. (For filesystems that provide page_mkwrite, there hasn't been a file_update_time call in the core code for several kernel versions.) --Andy -- 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/