[PATCH net-next 2/6] ionic: implement Rx page reuse

[Shannon Nelson <snelson@pensando.io>]

Rework the Rx buffer allocations to use pages twice when using
normal MTU in order to cut down on buffer allocation and mapping
overhead.

Instead of tracking individual pages, in which we may have
wasted half the space when using standard 1500 MTU, we track
buffers which use half pages, so we can use the second half
of the page rather than allocate and map a new page once the
first buffer has been used.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
---
 .../net/ethernet/pensando/ionic/ionic_dev.h   |  12 +-
 .../net/ethernet/pensando/ionic/ionic_txrx.c  | 215 +++++++++++-------
 2 files changed, 138 insertions(+), 89 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_dev.h b/drivers/net/ethernet/pensando/ionic/ionic_dev.h
index 690768ff0143..0f877c86eba6 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_dev.h
+++ b/drivers/net/ethernet/pensando/ionic/ionic_dev.h
@@ -170,9 +170,15 @@ typedef void (*ionic_desc_cb)(struct ionic_queue *q,
 			      struct ionic_desc_info *desc_info,
 			      struct ionic_cq_info *cq_info, void *cb_arg);
 
-struct ionic_page_info {
+#define IONIC_PAGE_SIZE				PAGE_SIZE
+#define IONIC_PAGE_SPLIT_SZ			(PAGE_SIZE / 2)
+#define IONIC_PAGE_GFP_MASK			(GFP_ATOMIC | __GFP_NOWARN |\
+						 __GFP_COMP | __GFP_MEMALLOC)
+
+struct ionic_buf_info {
 	struct page *page;
 	dma_addr_t dma_addr;
+	u32 page_offset;
 };
 
 struct ionic_desc_info {
@@ -187,8 +193,8 @@ struct ionic_desc_info {
 		struct ionic_txq_sg_desc *txq_sg_desc;
 		struct ionic_rxq_sg_desc *rxq_sgl_desc;
 	};
-	unsigned int npages;
-	struct ionic_page_info pages[IONIC_RX_MAX_SG_ELEMS + 1];
+	unsigned int nbufs;
+	struct ionic_buf_info bufs[IONIC_RX_MAX_SG_ELEMS + 1];
 	ionic_desc_cb cb;
 	void *cb_arg;
 };
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index 70b997f302ac..3e13cfee9ecd 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -54,7 +54,7 @@ static struct sk_buff *ionic_rx_skb_alloc(struct ionic_queue *q,
 	if (frags)
 		skb = napi_get_frags(&q_to_qcq(q)->napi);
 	else
-		skb = netdev_alloc_skb_ip_align(netdev, len);
+		skb = napi_alloc_skb(&q_to_qcq(q)->napi, len);
 
 	if (unlikely(!skb)) {
 		net_warn_ratelimited("%s: SKB alloc failed on %s!\n",
@@ -66,8 +66,15 @@ static struct sk_buff *ionic_rx_skb_alloc(struct ionic_queue *q,
 	return skb;
 }
 
+static void ionic_rx_buf_reset(struct ionic_buf_info *buf_info)
+{
+	buf_info->page = NULL;
+	buf_info->page_offset = 0;
+	buf_info->dma_addr = 0;
+}
+
 static int ionic_rx_page_alloc(struct ionic_queue *q,
-			       struct ionic_page_info *page_info)
+			       struct ionic_buf_info *buf_info)
 {
 	struct ionic_lif *lif = q->lif;
 	struct ionic_rx_stats *stats;
@@ -78,26 +85,26 @@ static int ionic_rx_page_alloc(struct ionic_queue *q,
 	dev = lif->ionic->dev;
 	stats = q_to_rx_stats(q);
 
-	if (unlikely(!page_info)) {
-		net_err_ratelimited("%s: %s invalid page_info in alloc\n",
+	if (unlikely(!buf_info)) {
+		net_err_ratelimited("%s: %s invalid buf_info in alloc\n",
 				    netdev->name, q->name);
 		return -EINVAL;
 	}
 
-	page_info->page = dev_alloc_page();
-	if (unlikely(!page_info->page)) {
+	buf_info->page = alloc_pages(IONIC_PAGE_GFP_MASK, 0);
+	if (unlikely(!buf_info->page)) {
 		net_err_ratelimited("%s: %s page alloc failed\n",
 				    netdev->name, q->name);
 		stats->alloc_err++;
 		return -ENOMEM;
 	}
+	buf_info->page_offset = 0;
 
-	page_info->dma_addr = dma_map_page(dev, page_info->page, 0, PAGE_SIZE,
-					   DMA_FROM_DEVICE);
-	if (unlikely(dma_mapping_error(dev, page_info->dma_addr))) {
-		put_page(page_info->page);
-		page_info->dma_addr = 0;
-		page_info->page = NULL;
+	buf_info->dma_addr = dma_map_page(dev, buf_info->page, buf_info->page_offset,
+					  IONIC_PAGE_SIZE, DMA_FROM_DEVICE);
+	if (unlikely(dma_mapping_error(dev, buf_info->dma_addr))) {
+		__free_pages(buf_info->page, 0);
+		ionic_rx_buf_reset(buf_info);
 		net_err_ratelimited("%s: %s dma map failed\n",
 				    netdev->name, q->name);
 		stats->dma_map_err++;
@@ -108,32 +115,46 @@ static int ionic_rx_page_alloc(struct ionic_queue *q,
 }
 
 static void ionic_rx_page_free(struct ionic_queue *q,
-			       struct ionic_page_info *page_info)
+			       struct ionic_buf_info *buf_info)
 {
-	struct ionic_lif *lif = q->lif;
-	struct net_device *netdev;
-	struct device *dev;
-
-	netdev = lif->netdev;
-	dev = lif->ionic->dev;
+	struct net_device *netdev = q->lif->netdev;
+	struct device *dev = q->lif->ionic->dev;
 
-	if (unlikely(!page_info)) {
-		net_err_ratelimited("%s: %s invalid page_info in free\n",
+	if (unlikely(!buf_info)) {
+		net_err_ratelimited("%s: %s invalid buf_info in free\n",
 				    netdev->name, q->name);
 		return;
 	}
 
-	if (unlikely(!page_info->page)) {
-		net_err_ratelimited("%s: %s invalid page in free\n",
-				    netdev->name, q->name);
+	if (!buf_info->page)
 		return;
-	}
 
-	dma_unmap_page(dev, page_info->dma_addr, PAGE_SIZE, DMA_FROM_DEVICE);
+	dma_unmap_page(dev, buf_info->dma_addr, IONIC_PAGE_SIZE, DMA_FROM_DEVICE);
+	__free_pages(buf_info->page, 0);
+	ionic_rx_buf_reset(buf_info);
+}
+
+static bool ionic_rx_buf_recycle(struct ionic_queue *q,
+				 struct ionic_buf_info *buf_info, u32 used)
+{
+	u32 size;
+
+	/* don't re-use pages allocated in low-mem condition */
+	if (page_is_pfmemalloc(buf_info->page))
+		return false;
+
+	/* don't re-use buffers from non-local numa nodes */
+	if (page_to_nid(buf_info->page) != numa_mem_id())
+		return false;
+
+	size = ALIGN(used, IONIC_PAGE_SPLIT_SZ);
+	buf_info->page_offset += size;
+	if (buf_info->page_offset >= IONIC_PAGE_SIZE)
+		return false;
+
+	get_page(buf_info->page);
 
-	put_page(page_info->page);
-	page_info->dma_addr = 0;
-	page_info->page = NULL;
+	return true;
 }
 
 static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
@@ -142,16 +163,16 @@ static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
 {
 	struct ionic_rxq_comp *comp = cq_info->cq_desc;
 	struct device *dev = q->lif->ionic->dev;
-	struct ionic_page_info *page_info;
+	struct ionic_buf_info *buf_info;
 	struct sk_buff *skb;
 	unsigned int i;
 	u16 frag_len;
 	u16 len;
 
-	page_info = &desc_info->pages[0];
+	buf_info = &desc_info->bufs[0];
 	len = le16_to_cpu(comp->len);
 
-	prefetch(page_address(page_info->page) + NET_IP_ALIGN);
+	prefetch(buf_info->page);
 
 	skb = ionic_rx_skb_alloc(q, len, true);
 	if (unlikely(!skb))
@@ -159,7 +180,7 @@ static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
 
 	i = comp->num_sg_elems + 1;
 	do {
-		if (unlikely(!page_info->page)) {
+		if (unlikely(!buf_info->page)) {
 			struct napi_struct *napi = &q_to_qcq(q)->napi;
 
 			napi->skb = NULL;
@@ -167,15 +188,25 @@ static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
 			return NULL;
 		}
 
-		frag_len = min(len, (u16)PAGE_SIZE);
+		frag_len = min_t(u16, len, IONIC_PAGE_SIZE - buf_info->page_offset);
 		len -= frag_len;
 
-		dma_unmap_page(dev, dma_unmap_addr(page_info, dma_addr),
-			       PAGE_SIZE, DMA_FROM_DEVICE);
+		dma_sync_single_for_cpu(dev,
+					buf_info->dma_addr + buf_info->page_offset,
+					frag_len, DMA_FROM_DEVICE);
+
 		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
-				page_info->page, 0, frag_len, PAGE_SIZE);
-		page_info->page = NULL;
-		page_info++;
+				buf_info->page, buf_info->page_offset, frag_len,
+				IONIC_PAGE_SIZE);
+
+		if (!ionic_rx_buf_recycle(q, buf_info, frag_len)) {
+			dma_unmap_page(dev, buf_info->dma_addr,
+				       IONIC_PAGE_SIZE, DMA_FROM_DEVICE);
+			ionic_rx_buf_reset(buf_info);
+		}
+
+		buf_info++;
+
 		i--;
 	} while (i > 0);
 
@@ -188,26 +219,26 @@ static struct sk_buff *ionic_rx_copybreak(struct ionic_queue *q,
 {
 	struct ionic_rxq_comp *comp = cq_info->cq_desc;
 	struct device *dev = q->lif->ionic->dev;
-	struct ionic_page_info *page_info;
+	struct ionic_buf_info *buf_info;
 	struct sk_buff *skb;
 	u16 len;
 
-	page_info = &desc_info->pages[0];
+	buf_info = &desc_info->bufs[0];
 	len = le16_to_cpu(comp->len);
 
 	skb = ionic_rx_skb_alloc(q, len, false);
 	if (unlikely(!skb))
 		return NULL;
 
-	if (unlikely(!page_info->page)) {
+	if (unlikely(!buf_info->page)) {
 		dev_kfree_skb(skb);
 		return NULL;
 	}
 
-	dma_sync_single_for_cpu(dev, dma_unmap_addr(page_info, dma_addr),
+	dma_sync_single_for_cpu(dev, buf_info->dma_addr + buf_info->page_offset,
 				len, DMA_FROM_DEVICE);
-	skb_copy_to_linear_data(skb, page_address(page_info->page), len);
-	dma_sync_single_for_device(dev, dma_unmap_addr(page_info, dma_addr),
+	skb_copy_to_linear_data(skb, page_address(buf_info->page) + buf_info->page_offset, len);
+	dma_sync_single_for_device(dev, buf_info->dma_addr + buf_info->page_offset,
 				   len, DMA_FROM_DEVICE);
 
 	skb_put(skb, len);
@@ -327,64 +358,73 @@ void ionic_rx_fill(struct ionic_queue *q)
 {
 	struct net_device *netdev = q->lif->netdev;
 	struct ionic_desc_info *desc_info;
-	struct ionic_page_info *page_info;
 	struct ionic_rxq_sg_desc *sg_desc;
 	struct ionic_rxq_sg_elem *sg_elem;
+	struct ionic_buf_info *buf_info;
 	struct ionic_rxq_desc *desc;
+	unsigned int max_sg_elems;
 	unsigned int remain_len;
-	unsigned int seg_len;
+	unsigned int frag_len;
 	unsigned int nfrags;
 	unsigned int i, j;
 	unsigned int len;
 
 	len = netdev->mtu + ETH_HLEN + VLAN_HLEN;
-	nfrags = round_up(len, PAGE_SIZE) / PAGE_SIZE;
+	max_sg_elems = q->lif->qtype_info[IONIC_QTYPE_RXQ].max_sg_elems;
 
 	for (i = ionic_q_space_avail(q); i; i--) {
+		nfrags = 0;
 		remain_len = len;
 		desc_info = &q->info[q->head_idx];
 		desc = desc_info->desc;
-		sg_desc = desc_info->sg_desc;
-		page_info = &desc_info->pages[0];
+		buf_info = &desc_info->bufs[0];
 
-		if (page_info->page) { /* recycle the buffer */
-			ionic_rxq_post(q, false, ionic_rx_clean, NULL);
-			continue;
-		}
-
-		/* fill main descriptor - pages[0] */
-		desc->opcode = (nfrags > 1) ? IONIC_RXQ_DESC_OPCODE_SG :
-					      IONIC_RXQ_DESC_OPCODE_SIMPLE;
-		desc_info->npages = nfrags;
-		if (unlikely(ionic_rx_page_alloc(q, page_info))) {
-			desc->addr = 0;
-			desc->len = 0;
-			return;
+		if (!buf_info->page) { /* alloc a new buffer? */
+			if (unlikely(ionic_rx_page_alloc(q, buf_info))) {
+				desc->addr = 0;
+				desc->len = 0;
+				return;
+			}
 		}
-		desc->addr = cpu_to_le64(page_info->dma_addr);
-		seg_len = min_t(unsigned int, PAGE_SIZE, len);
-		desc->len = cpu_to_le16(seg_len);
-		remain_len -= seg_len;
-		page_info++;
 
-		/* fill sg descriptors - pages[1..n] */
-		for (j = 0; j < nfrags - 1; j++) {
-			if (page_info->page) /* recycle the sg buffer */
-				continue;
+		/* fill main descriptor - buf[0] */
+		desc->addr = cpu_to_le64(buf_info->dma_addr + buf_info->page_offset);
+		frag_len = min_t(u16, len, IONIC_PAGE_SIZE - buf_info->page_offset);
+		desc->len = cpu_to_le16(frag_len);
+		remain_len -= frag_len;
+		buf_info++;
+		nfrags++;
 
+		/* fill sg descriptors - buf[1..n] */
+		sg_desc = desc_info->sg_desc;
+		for (j = 0; remain_len > 0 && j < max_sg_elems; j++) {
 			sg_elem = &sg_desc->elems[j];
-			if (unlikely(ionic_rx_page_alloc(q, page_info))) {
-				sg_elem->addr = 0;
-				sg_elem->len = 0;
-				return;
+			if (!buf_info->page) { /* alloc a new sg buffer? */
+				if (unlikely(ionic_rx_page_alloc(q, buf_info))) {
+					sg_elem->addr = 0;
+					sg_elem->len = 0;
+					return;
+				}
 			}
-			sg_elem->addr = cpu_to_le64(page_info->dma_addr);
-			seg_len = min_t(unsigned int, PAGE_SIZE, remain_len);
-			sg_elem->len = cpu_to_le16(seg_len);
-			remain_len -= seg_len;
-			page_info++;
+
+			sg_elem->addr = cpu_to_le64(buf_info->dma_addr + buf_info->page_offset);
+			frag_len = min_t(u16, remain_len, IONIC_PAGE_SIZE - buf_info->page_offset);
+			sg_elem->len = cpu_to_le16(frag_len);
+			remain_len -= frag_len;
+			buf_info++;
+			nfrags++;
 		}
 
+		/* clear end sg element as a sentinel */
+		if (j < max_sg_elems) {
+			sg_elem = &sg_desc->elems[j];
+			memset(sg_elem, 0, sizeof(*sg_elem));
+		}
+
+		desc->opcode = (nfrags > 1) ? IONIC_RXQ_DESC_OPCODE_SG :
+					      IONIC_RXQ_DESC_OPCODE_SIMPLE;
+		desc_info->nbufs = nfrags;
+
 		ionic_rxq_post(q, false, ionic_rx_clean, NULL);
 	}
 
@@ -395,21 +435,24 @@ void ionic_rx_fill(struct ionic_queue *q)
 void ionic_rx_empty(struct ionic_queue *q)
 {
 	struct ionic_desc_info *desc_info;
-	struct ionic_page_info *page_info;
+	struct ionic_buf_info *buf_info;
 	unsigned int i, j;
 
 	for (i = 0; i < q->num_descs; i++) {
 		desc_info = &q->info[i];
 		for (j = 0; j < IONIC_RX_MAX_SG_ELEMS + 1; j++) {
-			page_info = &desc_info->pages[j];
-			if (page_info->page)
-				ionic_rx_page_free(q, page_info);
+			buf_info = &desc_info->bufs[j];
+			if (buf_info->page)
+				ionic_rx_page_free(q, buf_info);
 		}
 
-		desc_info->npages = 0;
+		desc_info->nbufs = 0;
 		desc_info->cb = NULL;
 		desc_info->cb_arg = NULL;
 	}
+
+	q->head_idx = 0;
+	q->tail_idx = 0;
 }
 
 static void ionic_dim_update(struct ionic_qcq *qcq)
-- 
2.17.1