net: hns3: use bounce buffer when rx page can not be reused

Currently rx page will be reused to receive future packet when
the stack releases the previous skb quickly. If the old page
can not be reused, a new page will be allocated and mapped,
which comsumes a lot of cpu when IOMMU is in the strict mode,
especially when the application and irq/NAPI happens to run on
the same cpu.

So allocate a new frag to memcpy the data to avoid the costly
IOMMU unmapping/mapping operation, and add "frag_alloc_err"
and "frag_alloc" stats in "ethtool -S ethX" cmd.

The throughput improves above 50% when running single thread of
iperf using TCP when IOMMU is in strict mode and iperf shares the
same cpu with irq/NAPI(rx_copybreak = 2048 and mtu = 1500).
Signed-off-by: NYunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: NGuangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c

@@ -450,6 +450,7 @@ static const struct hns3_dbg_item rx_queue_info_items[] = {
 	{ "HEAD", 2 },
 	{ "FBDNUM", 2 },
 	{ "PKTNUM", 2 },
+	{ "COPYBREAK", 2 },
 	{ "RING_EN", 2 },
 	{ "RX_RING_EN", 2 },
 	{ "BASE_ADDR", 10 },
@@ -481,6 +482,7 @@ static void hns3_dump_rx_queue_info(struct hns3_enet_ring *ring,
 
 	sprintf(result[j++], "%6u", readl_relaxed(ring->tqp->io_base +
 		HNS3_RING_RX_RING_PKTNUM_RECORD_REG));
+	sprintf(result[j++], "%9u", ring->rx_copybreak);
 
 	sprintf(result[j++], "%7s", readl_relaxed(ring->tqp->io_base +
 		HNS3_RING_EN_REG) ? "on" : "off");

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

@@ -3552,6 +3552,28 @@ static void hns3_nic_reuse_page(struct sk_buff *skb, int i,
 		   hns3_page_size(ring)) {
 		desc_cb->page_offset += truesize;
 		desc_cb->reuse_flag = 1;
+	} else if (frag_size <= ring->rx_copybreak) {
+		void *frag = napi_alloc_frag(frag_size);
+
+		if (unlikely(!frag)) {
+			u64_stats_update_begin(&ring->syncp);
+			ring->stats.frag_alloc_err++;
+			u64_stats_update_end(&ring->syncp);
+
+			hns3_rl_err(ring_to_netdev(ring),
+				    "failed to allocate rx frag\n");
+			goto out;
+		}
+
+		desc_cb->reuse_flag = 1;
+		memcpy(frag, desc_cb->buf + frag_offset, frag_size);
+		skb_add_rx_frag(skb, i, virt_to_page(frag),
+				offset_in_page(frag), frag_size, frag_size);
+
+		u64_stats_update_begin(&ring->syncp);
+		ring->stats.frag_alloc++;
+		u64_stats_update_end(&ring->syncp);
+		return;
 	}
 
 out:
@@ -4620,6 +4642,7 @@ static void hns3_ring_get_cfg(struct hnae3_queue *q, struct hns3_nic_priv *priv,
 		ring = &priv->ring[q->tqp_index + queue_num];
 		desc_num = priv->ae_handle->kinfo.num_rx_desc;
 		ring->queue_index = q->tqp_index;
+		ring->rx_copybreak = priv->rx_copybreak;
 	}
 
 	hnae3_set_bit(ring->flag, HNAE3_RING_TYPE_B, ring_type);

drivers/net/ethernet/hisilicon/hns3/hns3_enet.h

@@ -427,6 +427,8 @@ struct ring_stats {
 			u64 csum_complete;
 			u64 rx_multicast;
 			u64 non_reuse_pg;
+			u64 frag_alloc_err;
+			u64 frag_alloc;
 		};
 		__le16 csum;
 	};
@@ -478,6 +480,7 @@ struct hns3_enet_ring {
 		/* for Rx ring */
 		struct {
 			u32 pull_len;   /* memcpy len for current rx packet */
+			u32 rx_copybreak;
 			u32 frag_num;
 			/* first buffer address for current packet */
 			unsigned char *va;
@@ -569,6 +572,7 @@ struct hns3_nic_priv {
 	struct hns3_enet_coalesce tx_coal;
 	struct hns3_enet_coalesce rx_coal;
 	u32 tx_copybreak;
+	u32 rx_copybreak;
 };
 
 union l3_hdr_info {

drivers/net/ethernet/hisilicon/hns3/hns3_ethtool.c

@@ -71,6 +71,8 @@ static const struct hns3_stats hns3_rxq_stats[] = {
 	HNS3_TQP_STAT("csum_complete", csum_complete),
 	HNS3_TQP_STAT("multicast", rx_multicast),
 	HNS3_TQP_STAT("non_reuse_pg", non_reuse_pg),
+	HNS3_TQP_STAT("frag_alloc_err", frag_alloc_err),
+	HNS3_TQP_STAT("frag_alloc", frag_alloc),
 };
 
 #define HNS3_PRIV_FLAGS_LEN ARRAY_SIZE(hns3_priv_flags)
@@ -1610,6 +1612,9 @@ static int hns3_get_tunable(struct net_device *netdev,
 		/* all the tx rings have the same tx_copybreak */
 		*(u32 *)data = priv->tx_copybreak;
 		break;
+	case ETHTOOL_RX_COPYBREAK:
+		*(u32 *)data = priv->rx_copybreak;
+		break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;
@@ -1633,6 +1638,13 @@ static int hns3_set_tunable(struct net_device *netdev,
 		for (i = 0; i < h->kinfo.num_tqps; i++)
 			priv->ring[i].tx_copybreak = priv->tx_copybreak;
 
+		break;
+	case ETHTOOL_RX_COPYBREAK:
+		priv->rx_copybreak = *(u32 *)data;
+
+		for (i = h->kinfo.num_tqps; i < h->kinfo.num_tqps * 2; i++)
+			priv->ring[i].rx_copybreak = priv->rx_copybreak;
+
 		break;
 	default:
 		ret = -EOPNOTSUPP;