From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id 9FB7C7CA0 for ; Tue, 19 Jul 2016 18:46:47 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay2.corp.sgi.com (Postfix) with ESMTP id 637B2304043 for ; Tue, 19 Jul 2016 16:46:44 -0700 (PDT) Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net [150.101.137.141]) by cuda.sgi.com with ESMTP id PtJ3SlqiFlzQN5Vy for ; Tue, 19 Jul 2016 16:46:35 -0700 (PDT) Date: Wed, 20 Jul 2016 09:46:34 +1000 From: Dave Chinner Subject: Re: [PATCH 3/3] xfs: remove __arch_pack Message-ID: <20160719234633.GI16044@dastard> References: <1466754767-10657-1-git-send-email-hch@lst.de> <1466754767-10657-4-git-send-email-hch@lst.de> <478743f8-774f-d363-2e3e-40cd0963d8a1@sandeen.net> <20160718053746.GA16044@dastard> <20160719085208.GA21785@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160719085208.GA21785@lst.de> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Christoph Hellwig Cc: Eric Sandeen , xfs@oss.sgi.com On Tue, Jul 19, 2016 at 10:52:08AM +0200, Christoph Hellwig wrote: > > On Mon, Jul 18, 2016 at 03:37:46PM +1000, Dave Chinner wrote: > > > The reason I did this in the first place was a vague notion that unconditional > > > packing was harmful. > > > > > > http://digitalvampire.org/blog/index.php/2006/07/31/why-you-shouldnt-use-__attribute__packed/ > > > > > > "However, it's actively harmful to add the attribute to a structure that's > > > already going to be laid out with no padding." > > > ... > > > "gcc gets scared about unaligned accesses and generates six times as much code > > > (96 bytes vs. 16 bytes)! sparc64 goes similarly crazy, bloating from 12 bytes > > > to 52 bytes" > > > > > > I don't know if that's (still) correct or not, but that was the reason > > > for the selective __pack application way back when. Might be worth > > > investigating? > > > > Christoph? The first two ptches are fine, but more info is needed > > for this one... > > I don't have a sparc64 compiler to test unfortunately. But I can confirm > that on x86-64 xfs.o is bit to bit identical with or without the patch. OK, that's probably good enough to go with for now. Thanks for following up, Christoph. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs