From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q5JIn8bN142604 for ; Tue, 19 Jun 2012 13:49:08 -0500 Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id DMwYDCyHpsfgH7jA for ; Tue, 19 Jun 2012 11:49:07 -0700 (PDT) Date: Tue, 19 Jun 2012 14:48:59 -0400 From: Mike Snitzer Subject: Re: Ext4 and xfs problems in dm-thin on allocation and discard Message-ID: <20120619184858.GA8841@redhat.com> References: <4FDF9EBE.2030809@shiftmail.org> <20120619015745.GJ25389@dastard> <20120619031241.GA3884@redhat.com> <20120619131649.GA6811@redhat.com> <20120619133041.GB6811@redhat.com> <4FE0840F.2050704@shiftmail.org> <20120619144413.GA7225@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20120619144413.GA7225@redhat.com> 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 Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Spelic Cc: =?utf-8?B?THVrw6HFoQ==?= Czerner , device-mapper development , linux-ext4@vger.kernel.org, xfs@oss.sgi.com On Tue, Jun 19 2012 at 10:44am -0400, Mike Snitzer wrote: > On Tue, Jun 19 2012 at 9:52am -0400, > Spelic wrote: > > > I do not know what is the mechanism for which xfs cannot unmap > > blocks from dm-thin, but it really can't. > > If anyone has dm-thin installed he can try. This is 100% > > reproducible for me. > > I was initially surprised by this considering the thinp-test-suite does > test a compilebench workload against xfs and ext4 using online discard > (-o discard). > > But I just modified that test to use a thin-pool with 'ignore_discard' > and the test still passed on both ext4 and xfs. > > So there is more work needed in the thinp-test-suite to use blktrace > hooks to verify that discards are occuring when the compilebench > generated files are removed. > > I'll work through that and report back. blktrace shows discards for both xfs and ext4. But in general xfs is issuing discards with much smaller extents than ext4 does, e.g.: to the thin device: + 128 vs + 32 to the thin-pool's data device: + 120 vs + 16 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs