Merge branch 'mlxsw-use-page-pool-for-rx-buffers-allocation'

Petr Machata says:

====================
mlxsw: Use page pool for Rx buffers allocation

Amit Cohen  writes:

After using NAPI to process events from hardware, the next step is to
use page pool for Rx buffers allocation, which is also enhances
performance.

To simplify this change, first use page pool to allocate one continuous
buffer for each packet, later memory consumption can be improved by using
fragmented buffers.

This set significantly enhances mlxsw driver performance, CPU can handle
about 370% of the packets per second it previously handled.

The next planned improvement is using XDP to optimize telemetry.

Patch set overview:
Patches #1-#2 are small preparations for page pool usage
Patch #3 initializes page pool, but do not use it
Patch #4 converts the driver to use page pool for buffers allocations
Patch #5 is an optimization for buffer access
Patch #6 cleans up an unused structure
Patch #7 uses napi_consume_skb() as part of Tx completion
====================

Link: https://lore.kernel.org/r/cover.1718709196.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxsw/Kconfig

@@ -33,6 +33,7 @@ config MLXSW_CORE_THERMAL
 config MLXSW_PCI
 	tristate "PCI bus implementation for Mellanox Technologies Switch ASICs"
 	depends on PCI && HAS_IOMEM && MLXSW_CORE
+	select PAGE_POOL
 	default m
 	help
 	  This is PCI bus implementation for Mellanox Technologies Switch ASICs.

drivers/net/ethernet/mellanox/mlxsw/pci.c

@@ -13,6 +13,7 @@
 #include <linux/if_vlan.h>
 #include <linux/log2.h>
 #include <linux/string.h>
+#include <net/page_pool/helpers.h>
 
 #include "pci_hw.h"
 #include "pci.h"
@@ -61,15 +62,11 @@ struct mlxsw_pci_mem_item {
 };
 
 struct mlxsw_pci_queue_elem_info {
+	struct page *page;
 	char *elem; /* pointer to actual dma mapped element mem chunk */
-	union {
 	struct {
 		struct sk_buff *skb;
 	} sdq;
-		struct {
-			struct sk_buff *skb;
-		} rdq;
-	} u;
 };
 
 struct mlxsw_pci_queue {
@@ -88,10 +85,14 @@ struct mlxsw_pci_queue {
 			enum mlxsw_pci_cqe_v v;
 			struct mlxsw_pci_queue *dq;
 			struct napi_struct napi;
+			struct page_pool *page_pool;
 		} cq;
 		struct {
 			struct tasklet_struct tasklet;
 		} eq;
+		struct {
+			struct mlxsw_pci_queue *cq;
+		} rdq;
 	} u;
 };
 
@@ -335,6 +336,25 @@ static void mlxsw_pci_sdq_fini(struct mlxsw_pci *mlxsw_pci,
 	mlxsw_cmd_hw2sw_sdq(mlxsw_pci->core, q->num);
 }
 
+#define MLXSW_PCI_SKB_HEADROOM (NET_SKB_PAD + NET_IP_ALIGN)
+
+#define MLXSW_PCI_RX_BUF_SW_OVERHEAD		\
+		(MLXSW_PCI_SKB_HEADROOM +	\
+		SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
+static void
+mlxsw_pci_wqe_rx_frag_set(struct mlxsw_pci *mlxsw_pci, struct page *page,
+			  char *wqe, int index, size_t frag_len)
+{
+	dma_addr_t mapaddr;
+
+	mapaddr = page_pool_get_dma_addr(page);
+	mapaddr += MLXSW_PCI_SKB_HEADROOM;
+
+	mlxsw_pci_wqe_address_set(wqe, index, mapaddr);
+	mlxsw_pci_wqe_byte_count_set(wqe, index, frag_len);
+}
+
 static int mlxsw_pci_wqe_frag_map(struct mlxsw_pci *mlxsw_pci, char *wqe,
 				  int index, char *frag_data, size_t frag_len,
 				  int direction)
@@ -364,43 +384,47 @@ static void mlxsw_pci_wqe_frag_unmap(struct mlxsw_pci *mlxsw_pci, char *wqe,
 	dma_unmap_single(&pdev->dev, mapaddr, frag_len, direction);
 }
 
-static int mlxsw_pci_rdq_skb_alloc(struct mlxsw_pci *mlxsw_pci,
+static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *page,
-				   struct mlxsw_pci_queue_elem_info *elem_info,
+					       u16 byte_count)
-				   gfp_t gfp)
 {
-	size_t buf_len = MLXSW_PORT_MAX_MTU;
+	void *data = page_address(page);
-	char *wqe = elem_info->elem;
+	unsigned int allocated_size;
 	struct sk_buff *skb;
-	int err;
 
-	skb = __netdev_alloc_skb_ip_align(NULL, buf_len, gfp);
+	net_prefetch(data);
-	if (!skb)
+	allocated_size = page_size(page);
-		return -ENOMEM;
+	skb = napi_build_skb(data, allocated_size);
+	if (unlikely(!skb))
+		return ERR_PTR(-ENOMEM);
 
-	err = mlxsw_pci_wqe_frag_map(mlxsw_pci, wqe, 0, skb->data,
+	skb_reserve(skb, MLXSW_PCI_SKB_HEADROOM);
-				     buf_len, DMA_FROM_DEVICE);
+	skb_put(skb, byte_count);
-	if (err)
+	return skb;
-		goto err_frag_map;
-
-	elem_info->u.rdq.skb = skb;
-	return 0;
-
-err_frag_map:
-	dev_kfree_skb_any(skb);
-	return err;
 }
 
-static void mlxsw_pci_rdq_skb_free(struct mlxsw_pci *mlxsw_pci,
+static int mlxsw_pci_rdq_page_alloc(struct mlxsw_pci_queue *q,
 				    struct mlxsw_pci_queue_elem_info *elem_info)
 {
-	struct sk_buff *skb;
+	struct mlxsw_pci_queue *cq = q->u.rdq.cq;
-	char *wqe;
+	size_t buf_len = MLXSW_PORT_MAX_MTU;
+	char *wqe = elem_info->elem;
+	struct page *page;
 
-	skb = elem_info->u.rdq.skb;
+	page = page_pool_dev_alloc_pages(cq->u.cq.page_pool);
-	wqe = elem_info->elem;
+	if (unlikely(!page))
+		return -ENOMEM;
 
-	mlxsw_pci_wqe_frag_unmap(mlxsw_pci, wqe, 0, DMA_FROM_DEVICE);
+	mlxsw_pci_wqe_rx_frag_set(q->pci, page, wqe, 0, buf_len);
-	dev_kfree_skb_any(skb);
+	elem_info->page = page;
+	return 0;
+}
+
+static void mlxsw_pci_rdq_page_free(struct mlxsw_pci_queue *q,
+				    struct mlxsw_pci_queue_elem_info *elem_info)
+{
+	struct mlxsw_pci_queue *cq = q->u.rdq.cq;
+
+	page_pool_put_page(cq->u.cq.page_pool, elem_info->page, -1, false);
 }
 
 static int mlxsw_pci_rdq_init(struct mlxsw_pci *mlxsw_pci, char *mbox,
@@ -434,13 +458,14 @@ static int mlxsw_pci_rdq_init(struct mlxsw_pci *mlxsw_pci, char *mbox,
 
 	cq = mlxsw_pci_cq_get(mlxsw_pci, cq_num);
 	cq->u.cq.dq = q;
+	q->u.rdq.cq = cq;
 
 	mlxsw_pci_queue_doorbell_producer_ring(mlxsw_pci, q);
 
 	for (i = 0; i < q->count; i++) {
 		elem_info = mlxsw_pci_queue_elem_info_producer_get(q);
 		BUG_ON(!elem_info);
-		err = mlxsw_pci_rdq_skb_alloc(mlxsw_pci, elem_info, GFP_KERNEL);
+		err = mlxsw_pci_rdq_page_alloc(q, elem_info);
 		if (err)
 			goto rollback;
 		/* Everything is set up, ring doorbell to pass elem to HW */
@@ -453,8 +478,9 @@ static int mlxsw_pci_rdq_init(struct mlxsw_pci *mlxsw_pci, char *mbox,
 rollback:
 	for (i--; i >= 0; i--) {
 		elem_info = mlxsw_pci_queue_elem_info_get(q, i);
-		mlxsw_pci_rdq_skb_free(mlxsw_pci, elem_info);
+		mlxsw_pci_rdq_page_free(q, elem_info);
 	}
+	q->u.rdq.cq = NULL;
 	cq->u.cq.dq = NULL;
 	mlxsw_cmd_hw2sw_rdq(mlxsw_pci->core, q->num);
 
@@ -470,7 +496,7 @@ static void mlxsw_pci_rdq_fini(struct mlxsw_pci *mlxsw_pci,
 	mlxsw_cmd_hw2sw_rdq(mlxsw_pci->core, q->num);
 	for (i = 0; i < q->count; i++) {
 		elem_info = mlxsw_pci_queue_elem_info_get(q, i);
-		mlxsw_pci_rdq_skb_free(mlxsw_pci, elem_info);
+		mlxsw_pci_rdq_page_free(q, elem_info);
 	}
 }
 
@@ -515,7 +541,7 @@ static void mlxsw_pci_cqe_sdq_handle(struct mlxsw_pci *mlxsw_pci,
 				     struct mlxsw_pci_queue *q,
 				     u16 consumer_counter_limit,
 				     enum mlxsw_pci_cqe_v cqe_v,
-				     char *cqe)
+				     char *cqe, int budget)
 {
 	struct pci_dev *pdev = mlxsw_pci->pdev;
 	struct mlxsw_pci_queue_elem_info *elem_info;
@@ -526,8 +552,8 @@ static void mlxsw_pci_cqe_sdq_handle(struct mlxsw_pci *mlxsw_pci,
 
 	spin_lock(&q->lock);
 	elem_info = mlxsw_pci_queue_elem_info_consumer_get(q);
-	tx_info = mlxsw_skb_cb(elem_info->u.sdq.skb)->tx_info;
+	tx_info = mlxsw_skb_cb(elem_info->sdq.skb)->tx_info;
-	skb = elem_info->u.sdq.skb;
+	skb = elem_info->sdq.skb;
 	wqe = elem_info->elem;
 	for (i = 0; i < MLXSW_PCI_WQE_SG_ENTRIES; i++)
 		mlxsw_pci_wqe_frag_unmap(mlxsw_pci, wqe, i, DMA_TO_DEVICE);
@@ -541,8 +567,8 @@ static void mlxsw_pci_cqe_sdq_handle(struct mlxsw_pci *mlxsw_pci,
 	}
 
 	if (skb)
-		dev_kfree_skb_any(skb);
+		napi_consume_skb(skb, budget);
-	elem_info->u.sdq.skb = NULL;
+	elem_info->sdq.skb = NULL;
 
 	if (q->consumer_counter++ != consumer_counter_limit)
 		dev_dbg_ratelimited(&pdev->dev, "Consumer counter does not match limit in SDQ\n");
@@ -605,26 +631,38 @@ static void mlxsw_pci_cqe_rdq_handle(struct mlxsw_pci *mlxsw_pci,
 {
 	struct pci_dev *pdev = mlxsw_pci->pdev;
 	struct mlxsw_pci_queue_elem_info *elem_info;
+	struct mlxsw_pci_queue *cq = q->u.rdq.cq;
 	struct mlxsw_rx_info rx_info = {};
-	char wqe[MLXSW_PCI_WQE_SIZE];
 	struct sk_buff *skb;
+	struct page *page;
 	u16 byte_count;
 	int err;
 
 	elem_info = mlxsw_pci_queue_elem_info_consumer_get(q);
-	skb = elem_info->u.rdq.skb;
-	memcpy(wqe, elem_info->elem, MLXSW_PCI_WQE_SIZE);
 
 	if (q->consumer_counter++ != consumer_counter_limit)
 		dev_dbg_ratelimited(&pdev->dev, "Consumer counter does not match limit in RDQ\n");
 
-	err = mlxsw_pci_rdq_skb_alloc(mlxsw_pci, elem_info, GFP_ATOMIC);
+	byte_count = mlxsw_pci_cqe_byte_count_get(cqe);
+	if (mlxsw_pci_cqe_crc_get(cqe_v, cqe))
+		byte_count -= ETH_FCS_LEN;
+
+	page = elem_info->page;
+
+	err = mlxsw_pci_rdq_page_alloc(q, elem_info);
 	if (err) {
-		dev_err_ratelimited(&pdev->dev, "Failed to alloc skb for RDQ\n");
+		dev_err_ratelimited(&pdev->dev, "Failed to alloc page\n");
 		goto out;
 	}
 
-	mlxsw_pci_wqe_frag_unmap(mlxsw_pci, wqe, 0, DMA_FROM_DEVICE);
+	skb = mlxsw_pci_rdq_build_skb(page, byte_count);
+	if (IS_ERR(skb)) {
+		dev_err_ratelimited(&pdev->dev, "Failed to build skb for RDQ\n");
+		page_pool_recycle_direct(cq->u.cq.page_pool, page);
+		goto out;
+	}
+
+	skb_mark_for_recycle(skb);
 
 	if (mlxsw_pci_cqe_lag_get(cqe_v, cqe)) {
 		rx_info.is_lag = true;
@@ -657,10 +695,6 @@ static void mlxsw_pci_cqe_rdq_handle(struct mlxsw_pci *mlxsw_pci,
 
 	mlxsw_pci_skb_cb_ts_set(mlxsw_pci, skb, cqe_v, cqe);
 
-	byte_count = mlxsw_pci_cqe_byte_count_get(cqe);
-	if (mlxsw_pci_cqe_crc_get(cqe_v, cqe))
-		byte_count -= ETH_FCS_LEN;
-	skb_put(skb, byte_count);
 	mlxsw_core_skb_receive(mlxsw_pci->core, skb, &rx_info);
 
 out:
@@ -785,7 +819,7 @@ static int mlxsw_pci_napi_poll_cq_tx(struct napi_struct *napi, int budget)
 		mlxsw_pci_queue_doorbell_consumer_ring(mlxsw_pci, q);
 
 		mlxsw_pci_cqe_sdq_handle(mlxsw_pci, sdq,
-					 wqe_counter, q->u.cq.v, ncqe);
+					 wqe_counter, q->u.cq.v, ncqe, budget);
 
 		work_done++;
 	}
@@ -832,19 +866,54 @@ static void mlxsw_pci_cq_napi_setup(struct mlxsw_pci_queue *q,
 			       mlxsw_pci_napi_poll_cq_rx);
 		break;
 	}
-
-	napi_enable(&q->u.cq.napi);
 }
 
 static void mlxsw_pci_cq_napi_teardown(struct mlxsw_pci_queue *q)
 {
-	napi_disable(&q->u.cq.napi);
 	netif_napi_del(&q->u.cq.napi);
 }
 
+static int mlxsw_pci_cq_page_pool_init(struct mlxsw_pci_queue *q,
+				       enum mlxsw_pci_cq_type cq_type)
+{
+	struct page_pool_params pp_params = {};
+	struct mlxsw_pci *mlxsw_pci = q->pci;
+	struct page_pool *page_pool;
+	u32 max_pkt_size;
+
+	if (cq_type != MLXSW_PCI_CQ_RDQ)
+		return 0;
+
+	max_pkt_size = MLXSW_PORT_MAX_MTU + MLXSW_PCI_RX_BUF_SW_OVERHEAD;
+	pp_params.order = get_order(max_pkt_size);
+	pp_params.flags = PP_FLAG_DMA_MAP;
+	pp_params.pool_size = MLXSW_PCI_WQE_COUNT;
+	pp_params.nid = dev_to_node(&mlxsw_pci->pdev->dev);
+	pp_params.dev = &mlxsw_pci->pdev->dev;
+	pp_params.napi = &q->u.cq.napi;
+	pp_params.dma_dir = DMA_FROM_DEVICE;
+
+	page_pool = page_pool_create(&pp_params);
+	if (IS_ERR(page_pool))
+		return PTR_ERR(page_pool);
+
+	q->u.cq.page_pool = page_pool;
+	return 0;
+}
+
+static void mlxsw_pci_cq_page_pool_fini(struct mlxsw_pci_queue *q,
+					enum mlxsw_pci_cq_type cq_type)
+{
+	if (cq_type != MLXSW_PCI_CQ_RDQ)
+		return;
+
+	page_pool_destroy(q->u.cq.page_pool);
+}
+
 static int mlxsw_pci_cq_init(struct mlxsw_pci *mlxsw_pci, char *mbox,
 			     struct mlxsw_pci_queue *q)
 {
+	enum mlxsw_pci_cq_type cq_type = mlxsw_pci_cq_type(mlxsw_pci, q);
 	int i;
 	int err;
 
@@ -874,15 +943,29 @@ static int mlxsw_pci_cq_init(struct mlxsw_pci *mlxsw_pci, char *mbox,
 	err = mlxsw_cmd_sw2hw_cq(mlxsw_pci->core, mbox, q->num);
 	if (err)
 		return err;
-	mlxsw_pci_cq_napi_setup(q, mlxsw_pci_cq_type(mlxsw_pci, q));
+	mlxsw_pci_cq_napi_setup(q, cq_type);
+
+	err = mlxsw_pci_cq_page_pool_init(q, cq_type);
+	if (err)
+		goto err_page_pool_init;
+
+	napi_enable(&q->u.cq.napi);
 	mlxsw_pci_queue_doorbell_consumer_ring(mlxsw_pci, q);
 	mlxsw_pci_queue_doorbell_arm_consumer_ring(mlxsw_pci, q);
 	return 0;
+
+err_page_pool_init:
+	mlxsw_pci_cq_napi_teardown(q);
+	return err;
 }
 
 static void mlxsw_pci_cq_fini(struct mlxsw_pci *mlxsw_pci,
 			      struct mlxsw_pci_queue *q)
 {
+	enum mlxsw_pci_cq_type cq_type = mlxsw_pci_cq_type(mlxsw_pci, q);
+
+	napi_disable(&q->u.cq.napi);
+	mlxsw_pci_cq_page_pool_fini(q, cq_type);
 	mlxsw_pci_cq_napi_teardown(q);
 	mlxsw_cmd_hw2sw_cq(mlxsw_pci->core, q->num);
 }
@@ -1919,7 +2002,7 @@ static int mlxsw_pci_skb_transmit(void *bus_priv, struct sk_buff *skb,
 		goto unlock;
 	}
 	mlxsw_skb_cb(skb)->tx_info = *tx_info;
-	elem_info->u.sdq.skb = skb;
+	elem_info->sdq.skb = skb;
 
 	wqe = elem_info->elem;
 	mlxsw_pci_wqe_c_set(wqe, 1); /* always report completion */