[PATCH V5 net-next 2/2] net: fec: improve XDP_TX performance

From: Wei Fang
Date: Thu Aug 10 2023 - 02:53:00 EST

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Previous message: Wei Fang: "[PATCH V5 net-next 1/2] net: fec: add XDP_TX feature support"
In reply to: Wei Fang: "RE: [PATCH V5 net-next 1/2] net: fec: add XDP_TX feature support"
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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@imx8mpevk:~# ./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@imx8mpevk:~# ./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

Signed-off-by: Wei Fang <wei.fang@xxxxxxx>
Suggested-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
Suggested-by: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
---
V5 changes:
New patch. Separated from the first patch, to keep track of the changes
and improvements (suggested by Jesper).
---
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;
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);

--
2.25.1

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