On Thu, Aug 10, 2023 at 08:30:57PM +0800, Xuan Zhuo wrote:
> Currently, the virtio core will perform a dma operation for each
> buffer. Although, the same page may be operated multiple times.
>
> This patch, the driver does the dma operation and manages the dma
> address based the feature premapped of virtio core.
>
> This way, 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
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Hi Xuan Zhuo,
looks like this patch is causing regressions. Do you have time to debug
or should I revert?
> ---
> drivers/net/virtio_net.c | 228 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 202 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 486b5849033d..16adb5ef18f8 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -126,6 +126,14 @@ static const struct virtnet_stat_desc virtnet_rq_stats_desc[] = {
> #define VIRTNET_SQ_STATS_LEN ARRAY_SIZE(virtnet_sq_stats_desc)
> #define VIRTNET_RQ_STATS_LEN ARRAY_SIZE(virtnet_rq_stats_desc)
>
> +/* The dma information of pages allocated at a time. */
> +struct virtnet_rq_dma {
> + dma_addr_t addr;
> + u32 ref;
> + u16 len;
> + u16 need_sync;
> +};
> +
> /* Internal representation of a send virtqueue */
> struct send_queue {
> /* Virtqueue associated with this send _queue */
> @@ -175,6 +183,12 @@ struct receive_queue {
> char name[16];
>
> struct xdp_rxq_info xdp_rxq;
> +
> + /* Record the last dma info to free after new pages is allocated. */
> + struct virtnet_rq_dma *last_dma;
> +
> + /* Do dma by self */
> + bool do_dma;
> };
>
> /* This structure can contain rss message with maximum settings for indirection table and keysize
> @@ -549,6 +563,156 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> return skb;
> }
>
> +static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
> +{
> + struct page *page = virt_to_head_page(buf);
> + struct virtnet_rq_dma *dma;
> + void *head;
> + int offset;
> +
> + head = page_address(page);
> +
> + dma = head;
> +
> + --dma->ref;
> +
> + if (dma->ref) {
> + if (dma->need_sync && len) {
> + offset = buf - (head + sizeof(*dma));
> +
> + virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr, offset,
> + len, DMA_FROM_DEVICE);
> + }
> +
> + return;
> + }
> +
> + virtqueue_dma_unmap_single_attrs(rq->vq, dma->addr, dma->len,
> + DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
> + put_page(page);
> +}
> +
> +static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
> +{
> + void *buf;
> +
> + buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> + if (buf && rq->do_dma)
> + virtnet_rq_unmap(rq, buf, *len);
> +
> + return buf;
> +}
> +
> +static void *virtnet_rq_detach_unused_buf(struct receive_queue *rq)
> +{
> + void *buf;
> +
> + buf = virtqueue_detach_unused_buf(rq->vq);
> + if (buf && rq->do_dma)
> + virtnet_rq_unmap(rq, buf, 0);
> +
> + return buf;
> +}
> +
> +static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
> +{
> + struct virtnet_rq_dma *dma;
> + dma_addr_t addr;
> + u32 offset;
> + void *head;
> +
> + if (!rq->do_dma) {
> + sg_init_one(rq->sg, buf, len);
> + return;
> + }
> +
> + head = page_address(rq->alloc_frag.page);
> +
> + offset = buf - head;
> +
> + dma = head;
> +
> + addr = dma->addr - sizeof(*dma) + offset;
> +
> + sg_init_table(rq->sg, 1);
> + rq->sg[0].dma_address = addr;
> + rq->sg[0].length = len;
> +}
> +
> +static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> +{
> + struct page_frag *alloc_frag = &rq->alloc_frag;
> + struct virtnet_rq_dma *dma;
> + void *buf, *head;
> + dma_addr_t addr;
> +
> + if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
> + return NULL;
> +
> + head = page_address(alloc_frag->page);
> +
> + if (rq->do_dma) {
> + dma = head;
> +
> + /* new pages */
> + if (!alloc_frag->offset) {
> + if (rq->last_dma) {
> + /* Now, the new page is allocated, the last dma
> + * will not be used. So the dma can be unmapped
> + * if the ref is 0.
> + */
> + virtnet_rq_unmap(rq, rq->last_dma, 0);
> + rq->last_dma = NULL;
> + }
> +
> + dma->len = alloc_frag->size - sizeof(*dma);
> +
> + addr = virtqueue_dma_map_single_attrs(rq->vq, dma + 1,
> + dma->len, DMA_FROM_DEVICE, 0);
> + if (virtqueue_dma_mapping_error(rq->vq, addr))
> + return NULL;
> +
> + dma->addr = addr;
> + dma->need_sync = virtqueue_dma_need_sync(rq->vq, addr);
> +
> + /* Add a reference to dma to prevent the entire dma from
> + * being released during error handling. This reference
> + * will be freed after the pages are no longer used.
> + */
> + get_page(alloc_frag->page);
> + dma->ref = 1;
> + alloc_frag->offset = sizeof(*dma);
> +
> + rq->last_dma = dma;
> + }
> +
> + ++dma->ref;
> + }
> +
> + buf = head + alloc_frag->offset;
> +
> + get_page(alloc_frag->page);
> + alloc_frag->offset += size;
> +
> + return buf;
> +}
> +
> +static void virtnet_rq_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++) {
> + if (virtqueue_set_dma_premapped(vi->rq[i].vq))
> + continue;
> +
> + vi->rq[i].do_dma = true;
> + }
> +}
> +
> static void free_old_xmit_skbs(struct send_queue *sq, bool in_napi)
> {
> unsigned int len;
> @@ -835,7 +999,7 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
> void *buf;
> int off;
>
> - buf = virtqueue_get_buf(rq->vq, &buflen);
> + buf = virtnet_rq_get_buf(rq, &buflen, NULL);
> if (unlikely(!buf))
> goto err_buf;
>
> @@ -1126,7 +1290,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
> return -EINVAL;
>
> while (--*num_buf > 0) {
> - buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
> + buf = virtnet_rq_get_buf(rq, &len, &ctx);
> if (unlikely(!buf)) {
> pr_debug("%s: rx error: %d buffers out of %d missing\n",
> dev->name, *num_buf,
> @@ -1351,7 +1515,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> while (--num_buf) {
> int num_skb_frags;
>
> - buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
> + buf = virtnet_rq_get_buf(rq, &len, &ctx);
> if (unlikely(!buf)) {
> pr_debug("%s: rx error: %d buffers out of %d missing\n",
> dev->name, num_buf,
> @@ -1414,7 +1578,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> err_skb:
> put_page(page);
> while (num_buf-- > 1) {
> - buf = virtqueue_get_buf(rq->vq, &len);
> + buf = virtnet_rq_get_buf(rq, &len, NULL);
> if (unlikely(!buf)) {
> pr_debug("%s: rx error: %d buffers missing\n",
> dev->name, num_buf);
> @@ -1524,7 +1688,6 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
> static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
> gfp_t gfp)
> {
> - struct page_frag *alloc_frag = &rq->alloc_frag;
> char *buf;
> unsigned int xdp_headroom = virtnet_get_headroom(vi);
> void *ctx = (void *)(unsigned long)xdp_headroom;
> @@ -1533,17 +1696,21 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>
> len = SKB_DATA_ALIGN(len) +
> SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> - if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
> +
> + buf = virtnet_rq_alloc(rq, len, gfp);
> + if (unlikely(!buf))
> return -ENOMEM;
>
> - buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
> - get_page(alloc_frag->page);
> - alloc_frag->offset += len;
> - sg_init_one(rq->sg, buf + VIRTNET_RX_PAD + xdp_headroom,
> - vi->hdr_len + GOOD_PACKET_LEN);
> + virtnet_rq_init_one_sg(rq, buf + VIRTNET_RX_PAD + xdp_headroom,
> + vi->hdr_len + GOOD_PACKET_LEN);
> +
> err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> - if (err < 0)
> + if (err < 0) {
> + if (rq->do_dma)
> + virtnet_rq_unmap(rq, buf, 0);
> put_page(virt_to_head_page(buf));
> + }
> +
> return err;
> }
>
> @@ -1620,23 +1787,22 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> unsigned int headroom = virtnet_get_headroom(vi);
> unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
> unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
> - char *buf;
> + unsigned int len, hole;
> void *ctx;
> + char *buf;
> int err;
> - unsigned int len, hole;
>
> /* Extra tailroom is needed to satisfy XDP's assumption. This
> * means rx frags coalescing won't work, but consider we've
> * disabled GSO for XDP, it won't be a big issue.
> */
> len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
> - if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> +
> + buf = virtnet_rq_alloc(rq, len + room, gfp);
> + if (unlikely(!buf))
> return -ENOMEM;
>
> - buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
> buf += headroom; /* advance address leaving hole at front of pkt */
> - get_page(alloc_frag->page);
> - alloc_frag->offset += len + room;
> hole = alloc_frag->size - alloc_frag->offset;
> if (hole < len + room) {
> /* To avoid internal fragmentation, if there is very likely not
> @@ -1650,11 +1816,15 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> alloc_frag->offset += hole;
> }
>
> - sg_init_one(rq->sg, buf, len);
> + virtnet_rq_init_one_sg(rq, buf, len);
> +
> ctx = mergeable_len_to_ctx(len + room, headroom);
> err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> - if (err < 0)
> + if (err < 0) {
> + if (rq->do_dma)
> + virtnet_rq_unmap(rq, buf, 0);
> put_page(virt_to_head_page(buf));
> + }
>
> return err;
> }
> @@ -1775,13 +1945,13 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
> void *ctx;
>
> while (stats.packets < budget &&
> - (buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx))) {
> + (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
> receive_buf(vi, rq, buf, len, ctx, xdp_xmit, &stats);
> stats.packets++;
> }
> } else {
> while (stats.packets < budget &&
> - (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> + (buf = virtnet_rq_get_buf(rq, &len, NULL)) != NULL) {
> receive_buf(vi, rq, buf, len, NULL, xdp_xmit, &stats);
> stats.packets++;
> }
> @@ -3553,8 +3723,11 @@ static void free_receive_page_frags(struct virtnet_info *vi)
> {
> int i;
> for (i = 0; i < vi->max_queue_pairs; i++)
> - if (vi->rq[i].alloc_frag.page)
> + if (vi->rq[i].alloc_frag.page) {
> + if (vi->rq[i].do_dma && vi->rq[i].last_dma)
> + virtnet_rq_unmap(&vi->rq[i], vi->rq[i].last_dma, 0);
> put_page(vi->rq[i].alloc_frag.page);
> + }
> }
>
> static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> @@ -3591,9 +3764,10 @@ static void free_unused_bufs(struct virtnet_info *vi)
> }
>
> for (i = 0; i < vi->max_queue_pairs; i++) {
> - struct virtqueue *vq = vi->rq[i].vq;
> - while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> - virtnet_rq_free_unused_buf(vq, buf);
> + struct receive_queue *rq = &vi->rq[i];
> +
> + while ((buf = virtnet_rq_detach_unused_buf(rq)) != NULL)
> + virtnet_rq_free_unused_buf(rq->vq, buf);
> cond_resched();
> }
> }
> @@ -3767,6 +3941,8 @@ 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
