linux-kernel - Re: [PATCH V10 19/19] virtio

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Message-ID: <CACGkMEssZ8OSRX=9QNk7P7=A4y1uMeMANfBCvmqKTSoga0jEQg@mail.gmail.com>
Date: Thu, 25 Dec 2025 12:20:10 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Perez Martin <eperezma@...hat.com>
Cc: mst@...hat.com, xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V10 19/19] virtio_ring: add in order support

On Wed, Dec 24, 2025 at 4:06 PM Eugenio Perez Martin
<eperezma@...hat.com> wrote:
>
> On Wed, Dec 24, 2025 at 1:34 AM Jason Wang <jasowang@...hat.com> wrote:
> >
> > This patch implements in order support for both split virtqueue and
> > packed virtqueue. Performance could be gained for the device where the
> > memory access could be expensive (e.g vhost-net or a real PCI device):
> >
> > Benchmark with KVM guest:
> >
> > Vhost-net on the host: (pktgen + XDP_DROP):
> >
> >          in_order=off | in_order=on | +%
> >     TX:  4.51Mpps     | 5.30Mpps    | +17%
> >     RX:  3.47Mpps     | 3.61Mpps    | + 4%
> >
> > Vhost-user(testpmd) on the host: (pktgen/XDP_DROP):
> >
> > For split virtqueue:
> >
> >          in_order=off | in_order=on | +%
> >     TX:  5.60Mpps     | 5.60Mpps    | +0.0%
> >     RX:  9.16Mpps     | 9.61Mpps    | +4.9%
> >
> > For packed virtqueue:
> >
> >          in_order=off | in_order=on | +%
> >     TX:  5.60Mpps     | 5.70Mpps    | +1.7%
> >     RX:  10.6Mpps     | 10.8Mpps    | +1.8%
> >
> > Benchmark also shows no performance impact for in_order=off for queue
> > size with 256 and 1024.
> >
> > Signed-off-by: Jason Wang <jasowang@...hat.com>
> >
> > fix
>
> Extra "fix" here?

My bad, let me fix that.

>
> Reviewed-by: Eugenio Pérez <eperezma@...hat.com>
>
> Thanks!

[...]

> > +
> > +       if (unlikely(last_used >= num)) {
> > +               BAD_RING(vq, "id %u out of range\n", last_used);
> > +               return NULL;
> > +       }
>
> This check cannot be true, but it does not harm so it is totally ok to
> fix on top later.

Will fix this in V11.

Thanks