From: "Michael S. Tsirkin" <mst@redhat.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
Eduardo Habkost <ehabkost@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Max Reitz <mreitz@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, Fam Zheng <fam@euphon.net>,
Raphael Norwitz <raphael.norwitz@nutanix.com>
Subject: Re: [PATCH v4 1/5] virtio-pci: add virtio_pci_optimal_num_queues() helper
Date: Tue, 9 Jun 2020 11:37:56 -0400 [thread overview]
Message-ID: <20200609113745-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200528173555.5f079b70.cohuck@redhat.com>
On Thu, May 28, 2020 at 05:35:55PM +0200, Cornelia Huck wrote:
> On Wed, 27 May 2020 11:29:21 +0100
> Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> > Multi-queue devices achieve the best performance when each vCPU has a
> > dedicated queue. This ensures that virtqueue used notifications are
> > handled on the same vCPU that submitted virtqueue buffers. When another
> > vCPU handles the the notification an IPI will be necessary to wake the
> > submission vCPU and this incurs a performance overhead.
> >
> > Provide a helper function that virtio-pci devices will use in later
> > patches to automatically select the optimal number of queues.
> >
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> > hw/virtio/virtio-pci.h | 9 +++++++++
> > hw/virtio/virtio-pci.c | 7 +++++++
> > 2 files changed, 16 insertions(+)
>
> That looks like a good idea, since the policy can be easily tweaked in
> one place later.
>
> For ccw, I don't see a good way to arrive at an optimal number of
> queues. Is there something we should do for mmio? If yes, should this
> be a callback in VirtioBusClass?
Stefan do you plan to address this?
next prev parent reply other threads:[~2020-06-09 15:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 10:29 [PATCH v4 0/5] virtio-pci: enable blk and scsi multi-queue by default Stefan Hajnoczi
2020-05-27 10:29 ` [PATCH v4 1/5] virtio-pci: add virtio_pci_optimal_num_queues() helper Stefan Hajnoczi
2020-05-28 15:35 ` Cornelia Huck
2020-06-09 15:37 ` Michael S. Tsirkin [this message]
2020-07-06 13:25 ` Stefan Hajnoczi
2020-07-06 14:14 ` Cornelia Huck
2020-05-27 10:29 ` [PATCH v4 2/5] virtio-scsi: introduce a constant for fixed virtqueues Stefan Hajnoczi
2020-05-28 14:18 ` Pankaj Gupta
2020-05-28 15:22 ` Philippe Mathieu-Daudé
2020-05-31 2:43 ` Raphael Norwitz
2020-05-27 10:29 ` [PATCH v4 3/5] virtio-scsi: default num_queues to -smp N Stefan Hajnoczi
2020-05-27 10:38 ` Daniel P. Berrangé
2020-05-28 8:50 ` Stefan Hajnoczi
2020-05-27 10:29 ` [PATCH v4 4/5] virtio-blk: " Stefan Hajnoczi
2020-05-28 14:45 ` Pankaj Gupta
2020-05-27 10:29 ` [PATCH v4 5/5] vhost-user-blk: " Stefan Hajnoczi
2020-05-31 2:42 ` Raphael Norwitz
2020-06-09 15:36 ` Michael S. Tsirkin
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