Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753324AbdHJQqP (ORCPT ); Thu, 10 Aug 2017 12:46:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45356 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753107AbdHJQqN (ORCPT ); Thu, 10 Aug 2017 12:46:13 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D4C1B806D2 Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=pbonzini@redhat.com Subject: Re: [PATCH 2/2] virtio: virtio_scsi: Set can_queue to the length of the virtqueue. To: "Richard W.M. Jones" , jejb@linux.vnet.ibm.com Cc: martin.petersen@oracle.com, mst@redhat.com, jasowang@redhat.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, hch@lst.de References: <20170810164035.19963-1-rjones@redhat.com> <20170810164035.19963-3-rjones@redhat.com> From: Paolo Bonzini Message-ID: <9d89d5ad-ed28-41a4-e3b9-ac96a93cf46a@redhat.com> Date: Thu, 10 Aug 2017 18:46:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170810164035.19963-3-rjones@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 10 Aug 2017 16:46:13 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1447 Lines: 38 On 10/08/2017 18:40, Richard W.M. Jones wrote: > Since switching to blk-mq as the default in commit 5c279bd9e406 > ("scsi: default to scsi-mq"), virtio-scsi LUNs consume about 10x as > much kernel memory. > > qemu currently allocates a fixed 128 entry virtqueue. can_queue > currently is set to 1024. But with indirect descriptors, each command > in the queue takes 1 virtqueue entry, so the number of commands which > can be queued is equal to the length of the virtqueue. > > Note I intend to send a patch to qemu to allow the virtqueue size to > be configured from the qemu command line. You can clear .can_queue from the templates. Otherwise looks good. Paolo > Thanks Paolo Bonzini, Christoph Hellwig. > > Signed-off-by: Richard W.M. Jones > --- > drivers/scsi/virtio_scsi.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index 9be211d68b15..d6b4ff634c0d 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -972,6 +972,8 @@ static int virtscsi_probe(struct virtio_device *vdev) > if (err) > goto virtscsi_init_failed; > > + shost->can_queue = virtqueue_get_vring_size(vscsi->req_vqs[0].vq); > + > cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1; > shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue); > shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF; >