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Date: Thu, 10 Aug 2023 16:11:41 +0200
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Wei Fang <wei.fang@....com>, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, shenwei.wang@....com,
xiaoning.wang@....com, ast@...nel.org, daniel@...earbox.net,
hawk@...nel.org, john.fastabend@...il.com, larysa.zaremba@...el.com,
aleksander.lobakin@...el.com, jbrouer@...hat.com, netdev@...r.kernel.org
Cc: linux-imx@....com, linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH V5 net-next 2/2] net: fec: improve XDP_TX performance
On 10/08/2023 08.45, Wei Fang wrote:
> As suggested by Jesper and Alexander, we can avoid converting xdp_buff
> to xdp_frame in case of XDP_TX to save a bunch of CPU cycles, so that
> we can further improve the XDP_TX performance.
>
> Before this patch on i.MX8MP-EVK board, the performance shows as follows.
> root@...8mpevk:~# ./xdp2 eth0
> proto 17: 353918 pkt/s
> proto 17: 352923 pkt/s
> proto 17: 353900 pkt/s
> proto 17: 352672 pkt/s
> proto 17: 353912 pkt/s
> proto 17: 354219 pkt/s
>
> After applying this patch, the performance is improved.
> root@...8mpevk:~# ./xdp2 eth0
> proto 17: 369261 pkt/s
> proto 17: 369267 pkt/s
> proto 17: 369206 pkt/s
> proto 17: 369214 pkt/s
> proto 17: 369126 pkt/s
> proto 17: 369272 pkt/s
>
So approx 4.3% improvement.
> Signed-off-by: Wei Fang <wei.fang@....com>
> Suggested-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> Suggested-by: Jesper Dangaard Brouer <hawk@...nel.org>
> ---
> V5 changes:
> New patch. Separated from the first patch, to keep track of the changes
> and improvements (suggested by Jesper).
Thanks
> ---
> drivers/net/ethernet/freescale/fec.h | 5 +-
> drivers/net/ethernet/freescale/fec_main.c | 134 ++++++++++++----------
> 2 files changed, 73 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index 7bb02a9da2a6..a8fbcada6b01 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -552,10 +552,7 @@ enum fec_txbuf_type {
> };
>
> struct fec_tx_buffer {
> - union {
> - struct sk_buff *skb;
> - struct xdp_frame *xdp;
> - };
> + void *buf_p;
I want to hear Olek's (Alexander) oppinion on this void pointer circus.
The rest of the patch looks correct to me so:
Reviewed-by: Jesper Dangaard Brouer <hawk@...nel.org>
--Jesper
> enum fec_txbuf_type type;
> };
>
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index 30b01985be7c..ae6e41ad71b8 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -399,7 +399,7 @@ static void fec_dump(struct net_device *ndev)
> fec16_to_cpu(bdp->cbd_sc),
> fec32_to_cpu(bdp->cbd_bufaddr),
> fec16_to_cpu(bdp->cbd_datlen),
> - txq->tx_buf[index].skb);
> + txq->tx_buf[index].buf_p);
> bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
> index++;
> } while (bdp != txq->bd.base);
> @@ -656,7 +656,7 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
>
> index = fec_enet_get_bd_index(last_bdp, &txq->bd);
> /* Save skb pointer */
> - txq->tx_buf[index].skb = skb;
> + txq->tx_buf[index].buf_p = skb;
>
> /* Make sure the updates to rest of the descriptor are performed before
> * transferring ownership.
> @@ -862,7 +862,7 @@ static int fec_enet_txq_submit_tso(struct fec_enet_priv_tx_q *txq,
> }
>
> /* Save skb pointer */
> - txq->tx_buf[index].skb = skb;
> + txq->tx_buf[index].buf_p = skb;
>
> skb_tx_timestamp(skb);
> txq->bd.cur = bdp;
> @@ -959,27 +959,27 @@ static void fec_enet_bd_init(struct net_device *dev)
> fec32_to_cpu(bdp->cbd_bufaddr),
> fec16_to_cpu(bdp->cbd_datlen),
> DMA_TO_DEVICE);
> - if (txq->tx_buf[i].skb) {
> - dev_kfree_skb_any(txq->tx_buf[i].skb);
> - txq->tx_buf[i].skb = NULL;
> - }
> - } else {
> - if (bdp->cbd_bufaddr &&
> - txq->tx_buf[i].type == FEC_TXBUF_T_XDP_NDO)
> + if (txq->tx_buf[i].buf_p)
> + dev_kfree_skb_any(txq->tx_buf[i].buf_p);
> + } else if (txq->tx_buf[i].type == FEC_TXBUF_T_XDP_NDO) {
> + if (bdp->cbd_bufaddr)
> dma_unmap_single(&fep->pdev->dev,
> fec32_to_cpu(bdp->cbd_bufaddr),
> fec16_to_cpu(bdp->cbd_datlen),
> DMA_TO_DEVICE);
>
> - if (txq->tx_buf[i].xdp) {
> - xdp_return_frame(txq->tx_buf[i].xdp);
> - txq->tx_buf[i].xdp = NULL;
> - }
> + if (txq->tx_buf[i].buf_p)
> + xdp_return_frame(txq->tx_buf[i].buf_p);
> + } else {
> + struct page *page = txq->tx_buf[i].buf_p;
>
> - /* restore default tx buffer type: FEC_TXBUF_T_SKB */
> - txq->tx_buf[i].type = FEC_TXBUF_T_SKB;
> + if (page)
> + page_pool_put_page(page->pp, page, 0, false);
> }
>
> + txq->tx_buf[i].buf_p = NULL;
> + /* restore default tx buffer type: FEC_TXBUF_T_SKB */
> + txq->tx_buf[i].type = FEC_TXBUF_T_SKB;
> bdp->cbd_bufaddr = cpu_to_fec32(0);
> bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
> }
> @@ -1386,6 +1386,8 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
> struct netdev_queue *nq;
> int index = 0;
> int entries_free;
> + struct page *page;
> + int frame_len;
>
> fep = netdev_priv(ndev);
>
> @@ -1407,8 +1409,7 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
> index = fec_enet_get_bd_index(bdp, &txq->bd);
>
> if (txq->tx_buf[index].type == FEC_TXBUF_T_SKB) {
> - skb = txq->tx_buf[index].skb;
> - txq->tx_buf[index].skb = NULL;
> + skb = txq->tx_buf[index].buf_p;
> if (bdp->cbd_bufaddr &&
> !IS_TSO_HEADER(txq, fec32_to_cpu(bdp->cbd_bufaddr)))
> dma_unmap_single(&fep->pdev->dev,
> @@ -1427,18 +1428,24 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
> if (unlikely(!budget))
> break;
>
> - xdpf = txq->tx_buf[index].xdp;
> - if (bdp->cbd_bufaddr &&
> - txq->tx_buf[index].type == FEC_TXBUF_T_XDP_NDO)
> - dma_unmap_single(&fep->pdev->dev,
> - fec32_to_cpu(bdp->cbd_bufaddr),
> - fec16_to_cpu(bdp->cbd_datlen),
> - DMA_TO_DEVICE);
> + if (txq->tx_buf[index].type == FEC_TXBUF_T_XDP_NDO) {
> + xdpf = txq->tx_buf[index].buf_p;
> + if (bdp->cbd_bufaddr)
> + dma_unmap_single(&fep->pdev->dev,
> + fec32_to_cpu(bdp->cbd_bufaddr),
> + fec16_to_cpu(bdp->cbd_datlen),
> + DMA_TO_DEVICE);
> + } else {
> + page = txq->tx_buf[index].buf_p;
> + }
> +
> bdp->cbd_bufaddr = cpu_to_fec32(0);
> - if (unlikely(!xdpf)) {
> + if (unlikely(!txq->tx_buf[index].buf_p)) {
> txq->tx_buf[index].type = FEC_TXBUF_T_SKB;
> goto tx_buf_done;
> }
> +
> + frame_len = fec16_to_cpu(bdp->cbd_datlen);
> }
>
> /* Check for errors. */
> @@ -1462,7 +1469,7 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
> if (txq->tx_buf[index].type == FEC_TXBUF_T_SKB)
> ndev->stats.tx_bytes += skb->len;
> else
> - ndev->stats.tx_bytes += xdpf->len;
> + ndev->stats.tx_bytes += frame_len;
> }
>
> /* Deferred means some collisions occurred during transmit,
> @@ -1487,20 +1494,16 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget)
>
> /* Free the sk buffer associated with this last transmit */
> dev_kfree_skb_any(skb);
> + } else if (txq->tx_buf[index].type == FEC_TXBUF_T_XDP_NDO) {
> + xdp_return_frame_rx_napi(xdpf);
> } else {
> - if (txq->tx_buf[index].type == FEC_TXBUF_T_XDP_NDO) {
> - xdp_return_frame_rx_napi(xdpf);
> - } else {
> - struct page *page = virt_to_head_page(xdpf->data);
> -
> - page_pool_put_page(page->pp, page, 0, true);
> - }
> -
> - txq->tx_buf[index].xdp = NULL;
> - /* restore default tx buffer type: FEC_TXBUF_T_SKB */
> - txq->tx_buf[index].type = FEC_TXBUF_T_SKB;
> + page_pool_put_page(page->pp, page, 0, true);
> }
>
> + txq->tx_buf[index].buf_p = NULL;
> + /* restore default tx buffer type: FEC_TXBUF_T_SKB */
> + txq->tx_buf[index].type = FEC_TXBUF_T_SKB;
> +
> tx_buf_done:
> /* Make sure the update to bdp and tx_buf are performed
> * before dirty_tx
> @@ -3230,7 +3233,6 @@ static void fec_enet_free_buffers(struct net_device *ndev)
> {
> struct fec_enet_private *fep = netdev_priv(ndev);
> unsigned int i;
> - struct sk_buff *skb;
> struct fec_enet_priv_tx_q *txq;
> struct fec_enet_priv_rx_q *rxq;
> unsigned int q;
> @@ -3255,18 +3257,23 @@ static void fec_enet_free_buffers(struct net_device *ndev)
> kfree(txq->tx_bounce[i]);
> txq->tx_bounce[i] = NULL;
>
> + if (!txq->tx_buf[i].buf_p) {
> + txq->tx_buf[i].type = FEC_TXBUF_T_SKB;
> + continue;
> + }
> +
> if (txq->tx_buf[i].type == FEC_TXBUF_T_SKB) {
> - skb = txq->tx_buf[i].skb;
> - txq->tx_buf[i].skb = NULL;
> - dev_kfree_skb(skb);
> + dev_kfree_skb(txq->tx_buf[i].buf_p);
> + } else if (txq->tx_buf[i].type == FEC_TXBUF_T_XDP_NDO) {
> + xdp_return_frame(txq->tx_buf[i].buf_p);
> } else {
> - if (txq->tx_buf[i].xdp) {
> - xdp_return_frame(txq->tx_buf[i].xdp);
> - txq->tx_buf[i].xdp = NULL;
> - }
> + struct page *page = txq->tx_buf[i].buf_p;
>
> - txq->tx_buf[i].type = FEC_TXBUF_T_SKB;
> + page_pool_put_page(page->pp, page, 0, false);
> }
> +
> + txq->tx_buf[i].buf_p = NULL;
> + txq->tx_buf[i].type = FEC_TXBUF_T_SKB;
> }
> }
> }
> @@ -3789,13 +3796,14 @@ fec_enet_xdp_get_tx_queue(struct fec_enet_private *fep, int index)
>
> static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
> struct fec_enet_priv_tx_q *txq,
> - struct xdp_frame *frame,
> - u32 dma_sync_len, bool ndo_xmit)
> + void *frame, u32 dma_sync_len,
> + bool ndo_xmit)
> {
> unsigned int index, status, estatus;
> struct bufdesc *bdp;
> dma_addr_t dma_addr;
> int entries_free;
> + u16 frame_len;
>
> entries_free = fec_enet_get_free_txdesc_num(txq);
> if (entries_free < MAX_SKB_FRAGS + 1) {
> @@ -3811,30 +3819,36 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
> index = fec_enet_get_bd_index(bdp, &txq->bd);
>
> if (ndo_xmit) {
> - dma_addr = dma_map_single(&fep->pdev->dev, frame->data,
> - frame->len, DMA_TO_DEVICE);
> + struct xdp_frame *xdpf = frame;
> +
> + dma_addr = dma_map_single(&fep->pdev->dev, xdpf->data,
> + xdpf->len, DMA_TO_DEVICE);
> if (dma_mapping_error(&fep->pdev->dev, dma_addr))
> return -ENOMEM;
>
> + frame_len = xdpf->len;
> + txq->tx_buf[index].buf_p = xdpf;
> txq->tx_buf[index].type = FEC_TXBUF_T_XDP_NDO;
> } else {
> - struct page *page = virt_to_page(frame->data);
> + struct xdp_buff *xdpb = frame;
> + struct page *page;
>
> - dma_addr = page_pool_get_dma_addr(page) + sizeof(*frame) +
> - frame->headroom;
> + page = virt_to_page(xdpb->data);
> + dma_addr = page_pool_get_dma_addr(page) +
> + (xdpb->data - xdpb->data_hard_start);
> dma_sync_single_for_device(&fep->pdev->dev, dma_addr,
> dma_sync_len, DMA_BIDIRECTIONAL);
> + frame_len = xdpb->data_end - xdpb->data;
> + txq->tx_buf[index].buf_p = page;
> txq->tx_buf[index].type = FEC_TXBUF_T_XDP_TX;
> }
>
> - txq->tx_buf[index].xdp = frame;
> -
> status |= (BD_ENET_TX_INTR | BD_ENET_TX_LAST);
> if (fep->bufdesc_ex)
> estatus = BD_ENET_TX_INT;
>
> bdp->cbd_bufaddr = cpu_to_fec32(dma_addr);
> - bdp->cbd_datlen = cpu_to_fec16(frame->len);
> + bdp->cbd_datlen = cpu_to_fec16(frame_len);
>
> if (fep->bufdesc_ex) {
> struct bufdesc_ex *ebdp = (struct bufdesc_ex *)bdp;
> @@ -3875,14 +3889,10 @@ static int fec_enet_xdp_tx_xmit(struct fec_enet_private *fep,
> int cpu, struct xdp_buff *xdp,
> u32 dma_sync_len)
> {
> - struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp);
> struct fec_enet_priv_tx_q *txq;
> struct netdev_queue *nq;
> int queue, ret;
>
> - if (unlikely(!xdpf))
> - return -EFAULT;
> -
> queue = fec_enet_xdp_get_tx_queue(fep, cpu);
> txq = fep->tx_queue[queue];
> nq = netdev_get_tx_queue(fep->netdev, queue);
> @@ -3891,7 +3901,7 @@ static int fec_enet_xdp_tx_xmit(struct fec_enet_private *fep,
>
> /* Avoid tx timeout as XDP shares the queue with kernel stack */
> txq_trans_cond_update(nq);
> - ret = fec_enet_txq_xmit_frame(fep, txq, xdpf, dma_sync_len, false);
> + ret = fec_enet_txq_xmit_frame(fep, txq, xdp, dma_sync_len, false);
>
> __netif_tx_unlock(nq);
>
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