linux-kernel - 答复: [PATCH] virtio_ring: remove unnecessary to_vvq call in virtqueue_disable_cb

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Date:   Thu, 23 Jun 2022 00:21:59 +0000
From:   tomorrow Wang (王德明) 
        <wangdeming@...pur.com>
To:     "mst@...hat.com" <mst@...hat.com>
CC:     "jasowang@...hat.com" <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 答复: [PATCH] virtio_ring: remove unnecessary to_vvq call in virtqueue_disable_cb_packed

Hi，
  The  35c51e093d956f6d058e193711c8d424817a44a9 patch has  maked  a similar
change
  
> Re: [PATCH] virtio_ring: remove unnecessary to_vvq call in
> virtqueue_disable_cb_packed
> 
> On Wed, Jun 22, 2022 at 03:50:52AM -0400, Deming Wang wrote:
> > It passes '_vq' to virtqueue_use_indirect(), which still calls to_vvq
> > to get 'vq', let's directly pass 'vq'. It can avoid unnecessary call
> > of to_vvq in hot path.
> >
> > Signed-off-by: Deming Wang <wangdeming@...pur.com>
> 
> I do not see the point of any of these patches. Sorry.
> If this is supposed to be an optimization, post some numbers pls.
> 
> 
> > ---
> >  drivers/virtio/virtio_ring.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c
> > b/drivers/virtio/virtio_ring.c index 13a7348cedff..af2b7785ed77 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -1475,10 +1475,8 @@ static void
> *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
> >  	return ret;
> >  }
> >
> > -static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> > +static void virtqueue_disable_cb_packed(struct vring_virtqueue *vq)
> >  {
> > -	struct vring_virtqueue *vq = to_vvq(_vq);
> > -
> >  	if (vq->packed.event_flags_shadow !=
> VRING_PACKED_EVENT_FLAG_DISABLE) {
> >  		vq->packed.event_flags_shadow =
> VRING_PACKED_EVENT_FLAG_DISABLE;
> >  		vq->packed.vring.driver->flags =
> > @@ -2007,7 +2005,7 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> >  		return;
> >
> >  	if (vq->packed_ring)
> > -		virtqueue_disable_cb_packed(_vq);
> > +		virtqueue_disable_cb_packed(vq);
> >  	else
> >  		virtqueue_disable_cb_split(_vq);
> >  }
> > --
> > 2.27.0


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