Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988AbdHEPvH (ORCPT ); Sat, 5 Aug 2017 11:51:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41950 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751262AbdHEPvF (ORCPT ); Sat, 5 Aug 2017 11:51:05 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 71324883C0 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=rjones@redhat.com Date: Sat, 5 Aug 2017 16:51:03 +0100 From: "Richard W.M. Jones" To: Christoph Hellwig Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "Martin K. Petersen" , pbonzini@redhat.com Subject: Re: Increased memory usage with scsi-mq Message-ID: <20170805155103.GE20914@redhat.com> References: <20170804210035.GA10017@redhat.com> <20170805084436.GA14264@lst.de> <20170805092704.GD20914@redhat.com> <20170805133954.GA17694@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170805133954.GA17694@lst.de> User-Agent: Mutt/1.5.20 (2009-12-10) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Sat, 05 Aug 2017 15:51:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2110 Lines: 56 On Sat, Aug 05, 2017 at 03:39:54PM +0200, Christoph Hellwig wrote: > For now can you apply this testing patch to the guest kernel? > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index 9be211d68b15..0cbe2c882e1c 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -818,7 +818,7 @@ static struct scsi_host_template virtscsi_host_template_single = { > .eh_timed_out = virtscsi_eh_timed_out, > .slave_alloc = virtscsi_device_alloc, > > - .can_queue = 1024, > + .can_queue = 64, > .dma_boundary = UINT_MAX, > .use_clustering = ENABLE_CLUSTERING, > .target_alloc = virtscsi_target_alloc, > @@ -839,7 +839,7 @@ static struct scsi_host_template virtscsi_host_template_multi = { > .eh_timed_out = virtscsi_eh_timed_out, > .slave_alloc = virtscsi_device_alloc, > > - .can_queue = 1024, > + .can_queue = 64, > .dma_boundary = UINT_MAX, > .use_clustering = ENABLE_CLUSTERING, > .target_alloc = virtscsi_target_alloc, > @@ -983,7 +983,7 @@ static int virtscsi_probe(struct virtio_device *vdev) > shost->max_id = num_targets; > shost->max_channel = 0; > shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE; > - shost->nr_hw_queues = num_queues; > + shost->nr_hw_queues = 1; > > #ifdef CONFIG_BLK_DEV_INTEGRITY > if (virtio_has_feature(vdev, VIRTIO_SCSI_F_T10_PI)) { Yes, that's an improvement, although it's still a little way off the density possible the old way: With scsi-mq enabled: 175 disks * With this patch: 319 disks * With scsi-mq disabled: 1755 disks Also only the first two hunks are necessary. The kernel behaves exactly the same way with or without the third hunk (ie. num_queues must already be 1). Can I infer from this that qemu needs a way to specify the can_queue setting to the virtio-scsi driver in the guest kernel? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org