From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757252Ab2IDPCI (ORCPT ); Tue, 4 Sep 2012 11:02:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44224 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753352Ab2IDPCG (ORCPT ); Tue, 4 Sep 2012 11:02:06 -0400 Date: Tue, 4 Sep 2012 18:03:23 +0300 From: "Michael S. Tsirkin" To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, kvm@vger.kernel.org, rusty@rustcorp.com.au, jasowang@redhat.com, virtualization@lists.linux-foundation.org Subject: Re: [PATCH 5/5] virtio-scsi: introduce multiqueue support Message-ID: <20120904150323.GA15116@redhat.com> References: <1346154857-12487-1-git-send-email-pbonzini@redhat.com> <1346154857-12487-6-git-send-email-pbonzini@redhat.com> <20120904144754.GO9805@redhat.com> <5046167C.3070109@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5046167C.3070109@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 04, 2012 at 04:55:56PM +0200, Paolo Bonzini wrote: > Il 04/09/2012 16:47, Michael S. Tsirkin ha scritto: > >> > static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq, > >> > - struct virtqueue *vq) > >> > + struct virtqueue *vq, bool affinity) > >> > { > >> > spin_lock_init(&virtscsi_vq->vq_lock); > >> > virtscsi_vq->vq = vq; > >> > + if (affinity) > >> > + virtqueue_set_affinity(vq, virtqueue_get_queue_index(vq) - > >> > + VIRTIO_SCSI_VQ_BASE); > >> > } > >> > > > This means in practice if you have less virtqueues than CPUs, > > things are not going to work well, will they? > > Not particularly. It could be better or worse than single queue > depending on the workload. Well interrupts will go to CPU different from the one that sends commands so ... > > Any idea what to do? > > Two possibilities: > > 1) Add a stride argument to virtqueue_set_affinity, and make it equal to > the number of queues. > > 2) Make multiqueue the default in QEMU, and make the default number of > queues equal to the number of VCPUs. > > I was going for (2). > > Paolo 3. use per target queue if less targets than cpus? -- MST