Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753366AbaLAMDN (ORCPT ); Mon, 1 Dec 2014 07:03:13 -0500 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:50719 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051AbaLAMDL (ORCPT ); Mon, 1 Dec 2014 07:03:11 -0500 Date: Mon, 1 Dec 2014 13:02:58 +0100 From: Cornelia Huck To: "Michael S. Tsirkin" Cc: David Hildenbrand , linux-kernel@vger.kernel.org, David Miller , rusty@au1.ibm.com, nab@linux-iscsi.org, pbonzini@redhat.com, thuth@linux.vnet.ibm.com, Rusty Russell , virtualization@lists.linux-foundation.org, linux-api@vger.kernel.org Subject: Re: [PATCH v7 16/46] virtio_blk: v1.0 support Message-ID: <20141201130258.6f01c1e3.cornelia.huck@de.ibm.com> In-Reply-To: <20141201114645.GA17505@redhat.com> References: <1417359787-10138-1-git-send-email-mst@redhat.com> <1417359787-10138-17-git-send-email-mst@redhat.com> <20141201091641.3085e682@thinkpad-w530> <20141201092658.GC15607@redhat.com> <20141201123315.1b95d06f.cornelia.huck@de.ibm.com> <20141201114645.GA17505@redhat.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14120112-0009-0000-0000-000002354617 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 1 Dec 2014 13:46:45 +0200 "Michael S. Tsirkin" wrote: > On Mon, Dec 01, 2014 at 12:33:15PM +0100, Cornelia Huck wrote: > > On Mon, 1 Dec 2014 11:26:58 +0200 > > "Michael S. Tsirkin" wrote: > > > > > For some places on data path, it might be worth it > > > to cache the correct value e.g. as part of device > > > structure. This replaces a branch with a memory load, > > > so the gain would have to be measured, best done > > > separately? > > > > I think we'll want to do some measuring once the basic structure is > > in place anyway. > > What's meant by in place here? That this patchset is ready :) > > > We should make sure that e.g. s390 only takes minor > > hit due to all that swapping that is needed for standard-compliant > > devices. Caching the value might certainly help in some paths. > > Well, this is queued in linux-next for 3.19, so > now's the time to do it :) So much to do, so little time... I'm still feeling a bit uncomfortable with some of the changes (virtio-scsi etc.) as I have not been able to test them yet (as there's no converted qemu for these yet). The virtio-net and virtio-blk changes seem sane, though, and virtio-ccw should be fine as well. OTOH, it's not like we're introducing new external interfaces, so later rework should be fine. -- 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/