On Thu, 25 Jan 2024 11:39:20 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Tue, Jan 16, 2024 at 3:59 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > If the xsk is enabling, the xsk tx will share the send queue.
>
> Any reason for this? Technically, virtio-net can work as other NIC
> like 256 queues. There could be some work like optimizing the
> interrupt allocations etc.
Just like the logic of XDP_TX.
Now the virtio spec does not allow to add new dynamic queues.
As I know, most hypervisors just support few queues. The num of
queues is not bigger than the cpu num. So the best way is
to share the send queues.
Parav and I tried to introduce dynamic queues. But that is dropped.
Before that I think we can share the send queues.
>
> > But the xsk requires that the send queue use the premapped mode.
> > So the send queue must support premapped mode.
> >
> > command: pktgen_sample01_simple.sh -i eth0 -s 16/1400 -d 10.0.0.123 -m 00:16:3e:12:e1:3e -n 0 -p 100
> > machine: ecs.ebmg6e.26xlarge of Aliyun
> > cpu: Intel(R) Xeon(R) Platinum 8269CY CPU @ 2.50GHz
> > iommu mode: intel_iommu=on iommu.strict=1 iommu=nopt
> >
> > | iommu off | iommu on
> > ----------------------|-----------------------------------------------------
> > | 16 | 1400 | 16 | 1400
> > ----------------------|-----------------------------------------------------
> > Before: |1716796.00 | 1581829.00 | 390756.00 | 374493.00
> > After(premapped off): |1733794.00 | 1576259.00 | 390189.00 | 378128.00
> > After(premapped on): |1707107.00 | 1562917.00 | 385667.00 | 373584.00
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/net/virtio/main.c | 119 ++++++++++++++++++++++++++++----
> > drivers/net/virtio/virtio_net.h | 10 ++-
> > 2 files changed, 116 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> > index 4fbf612da235..53143f95a3a0 100644
> > --- a/drivers/net/virtio/main.c
> > +++ b/drivers/net/virtio/main.c
> > @@ -168,13 +168,39 @@ static struct xdp_frame *ptr_to_xdp(void *ptr)
> > return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
> > }
> >
> > +static void virtnet_sq_unmap_buf(struct virtnet_sq *sq, struct virtio_dma_head *dma)
> > +{
> > + int i;
> > +
> > + if (!dma)
> > + return;
> > +
> > + for (i = 0; i < dma->next; ++i)
> > + virtqueue_dma_unmap_single_attrs(sq->vq,
> > + dma->items[i].addr,
> > + dma->items[i].length,
> > + DMA_TO_DEVICE, 0);
> > + dma->next = 0;
> > +}
> > +
> > static void __free_old_xmit(struct virtnet_sq *sq, bool in_napi,
> > u64 *bytes, u64 *packets)
> > {
> > + struct virtio_dma_head *dma;
> > unsigned int len;
> > void *ptr;
> >
> > - while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
> > + if (virtqueue_get_dma_premapped(sq->vq)) {
>
> Any chance this.can be false?
__free_old_xmit is the common path.
The virtqueue_get_dma_premapped() is used to check whether the sq is premapped
mode.
>
> > + dma = &sq->dma.head;
> > + dma->num = ARRAY_SIZE(sq->dma.items);
> > + dma->next = 0;
>
> Btw, I found in the case of RX we have:
>
> virtnet_rq_alloc():
>
> alloc_frag->offset = sizeof(*dma);
>
> This seems to defeat frag coalescing when the memory is highly
> fragmented or high order allocation is disallowed.
>
> Any idea to solve this?
On the rq premapped pathset, I answered this.
http://lore.kernel.org/all/1692156147.7470396-3-xuanzhuo@xxxxxxxxxxxxxxxxx
>
> > + } else {
> > + dma = NULL;
> > + }
> > +
> > + while ((ptr = virtqueue_get_buf_ctx_dma(sq->vq, &len, dma, NULL)) != NULL) {
> > + virtnet_sq_unmap_buf(sq, dma);
> > +
> > if (!is_xdp_frame(ptr)) {
> > struct sk_buff *skb = ptr;
> >
> > @@ -572,16 +598,70 @@ static void *virtnet_rq_alloc(struct virtnet_rq *rq, u32 size, gfp_t gfp)
> > return buf;
> > }
> >
> > -static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > +static void virtnet_set_premapped(struct virtnet_info *vi)
> > {
> > int i;
> >
> > - /* disable for big mode */
> > - if (!vi->mergeable_rx_bufs && vi->big_packets)
> > - return;
> > + for (i = 0; i < vi->max_queue_pairs; i++) {
> > + virtqueue_set_dma_premapped(vi->sq[i].vq);
> >
> > - for (i = 0; i < vi->max_queue_pairs; i++)
> > - virtqueue_set_dma_premapped(vi->rq[i].vq);
> > + /* TODO for big mode */
>
> Btw, how hard to support big mode? If we can do premapping for that
> code could be simplified.
>
> (There are vendors that doesn't support mergeable rx buffers).
I will do that after these patch-sets
>
> > + if (vi->mergeable_rx_bufs || !vi->big_packets)
> > + virtqueue_set_dma_premapped(vi->rq[i].vq);
> > + }
> > +}
> > +
> > +static void virtnet_sq_unmap_sg(struct virtnet_sq *sq, u32 num)
> > +{
> > + struct scatterlist *sg;
> > + u32 i;
> > +
> > + for (i = 0; i < num; ++i) {
> > + sg = &sq->sg[i];
> > +
> > + virtqueue_dma_unmap_single_attrs(sq->vq,
> > + sg->dma_address,
> > + sg->length,
> > + DMA_TO_DEVICE, 0);
> > + }
> > +}
> > +
> > +static int virtnet_sq_map_sg(struct virtnet_sq *sq, u32 num)
> > +{
> > + struct scatterlist *sg;
> > + u32 i;
> > +
> > + for (i = 0; i < num; ++i) {
> > + sg = &sq->sg[i];
> > + sg->dma_address = virtqueue_dma_map_single_attrs(sq->vq, sg_virt(sg),
> > + sg->length,
> > + DMA_TO_DEVICE, 0);
> > + if (virtqueue_dma_mapping_error(sq->vq, sg->dma_address))
> > + goto err;
> > + }
> > +
>
> This seems nothing virtio-net specific, let's move it to the core?
This is the dma api style.
And the caller can not judge it by the return value of
virtqueue_dma_map_single_attrs.
Thanks
>
> Thanks
>
>
> > + return 0;
> > +
> > +err:
> > + virtnet_sq_unmap_sg(sq, i);
> > + return -ENOMEM;
> > +}
> > +
> > +static int virtnet_add_outbuf(struct virtnet_sq *sq, u32 num, void *data)
> > +{
> > + int ret;
> > +
> > + if (virtqueue_get_dma_premapped(sq->vq)) {
> > + ret = virtnet_sq_map_sg(sq, num);
> > + if (ret)
> > + return -ENOMEM;
> > + }
> > +
> > + ret = virtqueue_add_outbuf(sq->vq, sq->sg, num, data, GFP_ATOMIC);
> > + if (ret && virtqueue_get_dma_premapped(sq->vq))
> > + virtnet_sq_unmap_sg(sq, num);
> > +
> > + return ret;
> > }
> >
> > static void free_old_xmit(struct virtnet_sq *sq, bool in_napi)
> > @@ -687,8 +767,7 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
> > skb_frag_size(frag), skb_frag_off(frag));
> > }
> >
> > - err = virtqueue_add_outbuf(sq->vq, sq->sg, nr_frags + 1,
> > - xdp_to_ptr(xdpf), GFP_ATOMIC);
> > + err = virtnet_add_outbuf(sq, nr_frags + 1, xdp_to_ptr(xdpf));
> > if (unlikely(err))
> > return -ENOSPC; /* Caller handle free/refcnt */
> >
> > @@ -2154,7 +2233,7 @@ static int xmit_skb(struct virtnet_sq *sq, struct sk_buff *skb)
> > return num_sg;
> > num_sg++;
> > }
> > - return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
> > + return virtnet_add_outbuf(sq, num_sg, skb);
> > }
> >
> > static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> > @@ -4011,9 +4090,25 @@ static void free_receive_page_frags(struct virtnet_info *vi)
> >
> > static void virtnet_sq_free_unused_bufs(struct virtqueue *vq)
> > {
> > + struct virtnet_info *vi = vq->vdev->priv;
> > + struct virtio_dma_head *dma;
> > + struct virtnet_sq *sq;
> > + int i = vq2txq(vq);
> > void *buf;
> >
> > - while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
> > + sq = &vi->sq[i];
> > +
> > + if (virtqueue_get_dma_premapped(sq->vq)) {
> > + dma = &sq->dma.head;
> > + dma->num = ARRAY_SIZE(sq->dma.items);
> > + dma->next = 0;
> > + } else {
> > + dma = NULL;
> > + }
> > +
> > + while ((buf = virtqueue_detach_unused_buf_dma(vq, dma)) != NULL) {
> > + virtnet_sq_unmap_buf(sq, dma);
> > +
> > if (!is_xdp_frame(buf))
> > dev_kfree_skb(buf);
> > else
> > @@ -4228,7 +4323,7 @@ static int init_vqs(struct virtnet_info *vi)
> > if (ret)
> > goto err_free;
> >
> > - virtnet_rq_set_premapped(vi);
> > + virtnet_set_premapped(vi);
> >
> > cpus_read_lock();
> > virtnet_set_affinity(vi);
> > diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> > index 066a2b9d2b3c..dda144cc91c7 100644
> > --- a/drivers/net/virtio/virtio_net.h
> > +++ b/drivers/net/virtio/virtio_net.h
> > @@ -48,13 +48,21 @@ struct virtnet_rq_dma {
> > u16 need_sync;
> > };
> >
> > +struct virtnet_sq_dma {
> > + struct virtio_dma_head head;
> > + struct virtio_dma_item items[MAX_SKB_FRAGS + 2];
> > +};
> > +
> > /* Internal representation of a send virtqueue */
> > struct virtnet_sq {
> > /* Virtqueue associated with this virtnet_sq */
> > struct virtqueue *vq;
> >
> > /* TX: fragments + linear part + virtio header */
> > - struct scatterlist sg[MAX_SKB_FRAGS + 2];
> > + union {
> > + struct scatterlist sg[MAX_SKB_FRAGS + 2];
> > + struct virtnet_sq_dma dma;
> > + };
> >
> > /* Name of the send queue: output.$index */
> > char name[16];
> > --
> > 2.32.0.3.g01195cf9f
> >
>
