From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46245) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TaO8x-00062I-2E for qemu-devel@nongnu.org; Mon, 19 Nov 2012 04:59:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TaO8u-0007zw-0Y for qemu-devel@nongnu.org; Mon, 19 Nov 2012 04:59:55 -0500 Received: from mail.profihost.ag ([85.158.179.208]:38240) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TaO8t-0007zl-Mk for qemu-devel@nongnu.org; Mon, 19 Nov 2012 04:59:51 -0500 Message-ID: <50AA0314.6090208@profihost.ag> Date: Mon, 19 Nov 2012 10:59:48 +0100 From: Stefan Priebe - Profihost AG MIME-Version: 1.0 References: <589082222.7272963.1352241778123.JavaMail.root@redhat.com> <50A95A6A.4010109@profihost.ag> <50A9E991.2070609@redhat.com> <50A9FD86.3050400@profihost.ag> <50AA01C0.8030709@redhat.com> In-Reply-To: <50AA01C0.8030709@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] scsi-hd with discard_granularity and unmap results in Aborted Commands List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org Am 19.11.2012 10:54, schrieb Paolo Bonzini: > Il 19/11/2012 10:36, Stefan Priebe - Profihost AG ha scritto: >> Hi Paolo, >> >> Am 19.11.2012 09:10, schrieb Paolo Bonzini: >>>> I'm sorry the discard requests aren't failing. Qemu / Block driver >>>> starts to cancel a bunch of requests. >>> >>> That is being done in the kernel (the guest, I think) because the UNMAPs >>> are taking too long. >> >> That makes sense. RBD handles discards as buffered I/O. When i do an >> mkfs.xfs on a 30GB device i see around 900 pending discard requests. rbd >> finishes them all before reporting success. >> >> If it is correct that a 3.6.7 kernel sends as many discard requests i >> only the a solution in using unbuffered I/O for discards. >> >> Do you know what is the correct way? > > I think the correct fix is to serialize them in the kernel. So you mean this is not a bug in rbd or qemu this is a general bug in the linux kernel since they implemented discard? Greets, Stefan