Re: [PATCH v2 2/4] virtio-scsi: default num_queues to -smp N

[Stefan Hajnoczi]

On Tue, Feb 11, 2020 at 11:31:17AM -0500, Michael S. Tsirkin wrote:
> On Tue, Feb 11, 2020 at 04:20:41PM +0000, Stefan Hajnoczi wrote:
> > On Mon, Feb 03, 2020 at 12:39:49PM +0100, Sergio Lopez wrote:
> > > On Mon, Feb 03, 2020 at 10:57:44AM +0000, Daniel P. Berrangé wrote:
> > > > On Mon, Feb 03, 2020 at 11:25:29AM +0100, Sergio Lopez wrote:
> > > > > On Thu, Jan 30, 2020 at 10:52:35AM +0000, Stefan Hajnoczi wrote:
> > > > > > On Thu, Jan 30, 2020 at 01:29:16AM +0100, Paolo Bonzini wrote:
> > > > > > > On 29/01/20 16:44, Stefan Hajnoczi wrote:
> > > > > > > > On Mon, Jan 27, 2020 at 02:10:31PM +0100, Cornelia Huck wrote:
> > > > > > > >> On Fri, 24 Jan 2020 10:01:57 +0000
> > > > > > > >> Stefan Hajnoczi <address@hidden> wrote:
> > I will create a 32 vCPU guest with 100 virtio-blk devices and verify
> > that enabling multi-queue is successful.
> 
> and that it's helpful for performance?

I may be a little while before the next revision of this patch series.
Testing reveals scalability problems when creating so many virtqueues
:).

I've measured boot time, memory consumption, and random read IOPS.  They
are all significantly worse (32 vCPUs, 24 GB RAM, 101 virtio-blk
devices, 32 queues/device).

Time to see what's going on and whether some general scalability
improvements are possible here before we enable multi-queue by default.

Stefan

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