On Fri, 18 Oct 2024 16:00:07 +0800, Jason Wang <jasow...@redhat.com> wrote:
> On Mon, Oct 14, 2024 at 11:12 AM Xuan Zhuo <xuanz...@linux.alibaba.com> wrote:
> >
> > Currently, the virtio core will perform a dma operation for each
> > buffer. Although, the same page may be operated multiple times.
> >
> > In premapped mod, we can perform only one dma operation for the pages of
> > the alloc frag. This is beneficial for the iommu device.
> >
> > kernel command line: intel_iommu=on iommu.passthrough=0
> >
> > | strict=0 | strict=1
> > Before | 775496pps | 428614pps
> > After | 1109316pps | 742853pps
> >
> > In the 6.11, we disabled this feature because a regress [1].
> >
> > Now, we fix the problem and re-enable it.
> >
> > [1]:
> > http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540...@oracle.com
> >
> > Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
> > ---
> > drivers/net/virtio_net.c | 17 +++++++++++++++++
> > 1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index cd90e77881df..8cf24b7b58bd 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -6133,6 +6133,21 @@ static int virtnet_alloc_queues(struct virtnet_info
> > *vi)
> > return -ENOMEM;
> > }
> >
> > +static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > +{
> > + int i;
> > +
> > + /* disable for big mode */
> > + if (vi->mode == VIRTNET_MODE_BIG)
> > + return;
>
> Nitpick: I would like such a check to be done at the caller.
I am ok, if you like.
Thanks.
>
> But anyhow the patch looks good
>
> Acked-by: Jason Wang <jasow...@redhat.com>
>
> Thanks
>
> > +
> > + for (i = 0; i < vi->max_queue_pairs; i++) {
> > + /* error should never happen */
> > + BUG_ON(virtqueue_set_dma_premapped(vi->rq[i].vq));
> > + vi->rq[i].do_dma = true;
> > + }
> > +}
> > +
> > static int init_vqs(struct virtnet_info *vi)
> > {
> > int ret;
> > @@ -6146,6 +6161,8 @@ static int init_vqs(struct virtnet_info *vi)
> > if (ret)
> > goto err_free;
> >
> > + virtnet_rq_set_premapped(vi);
> > +
> > cpus_read_lock();
> > virtnet_set_affinity(vi);
> > cpus_read_unlock();
> > --
> > 2.32.0.3.g01195cf9f
> >
>
