net: aquantia: optimize rx performance by page reuse strategy

We introduce internal aq_rxpage wrapper over regular page
where extra field is tracked: rxpage offset inside of allocated page.

This offset allows to reuse one page for multiple packets.
When needed (for example with large frames processing), allocated
pageorder could be customized. This gives even larger page reuse
efficiency.

page_ref_count is used to track page users. If during rx refill
underlying page has users, we increase pg_off by rx frame size
thus the top half of the page is reused.

Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 121 insertions, 45 deletions

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
index 4558f16c0ca6..c48696123193 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_ring.c
@@ -12,10 +12,89 @@
 #include "aq_ring.h"
 #include "aq_nic.h"
 #include "aq_hw.h"
+#include "aq_hw_utils.h"
 
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 
+static inline void aq_free_rxpage(struct aq_rxpage *rxpage, struct device *dev)
+{
+	unsigned int len = PAGE_SIZE << rxpage->order;
+
+	dma_unmap_page(dev, rxpage->daddr, len, DMA_FROM_DEVICE);
+
+	/* Drop the ref for being in the ring. */
+	__free_pages(rxpage->page, rxpage->order);
+	rxpage->page = NULL;
+}
+
+static int aq_get_rxpage(struct aq_rxpage *rxpage, unsigned int order,
+			 struct device *dev)
+{
+	struct page *page;
+	dma_addr_t daddr;
+	int ret = -ENOMEM;
+
+	page = dev_alloc_pages(order);
+	if (unlikely(!page))
+		goto err_exit;
+
+	daddr = dma_map_page(dev, page, 0, PAGE_SIZE << order,
+			     DMA_FROM_DEVICE);
+
+	if (unlikely(dma_mapping_error(dev, daddr)))
+		goto free_page;
+
+	rxpage->page = page;
+	rxpage->daddr = daddr;
+	rxpage->order = order;
+	rxpage->pg_off = 0;
+
+	return 0;
+
+free_page:
+	__free_pages(page, order);
+
+err_exit:
+	return ret;
+}
+
+static int aq_get_rxpages(struct aq_ring_s *self, struct aq_ring_buff_s *rxbuf,
+			  int order)
+{
+	int ret;
+
+	if (rxbuf->rxdata.page) {
+		/* One means ring is the only user and can reuse */
+		if (page_ref_count(rxbuf->rxdata.page) > 1) {
+			/* Try reuse buffer */
+			rxbuf->rxdata.pg_off += AQ_CFG_RX_FRAME_MAX;
+			if (rxbuf->rxdata.pg_off + AQ_CFG_RX_FRAME_MAX <=
+				(PAGE_SIZE << order)) {
+				self->stats.rx.pg_flips++;
+			} else {
+				/* Buffer exhausted. We have other users and
+				 * should release this page and realloc
+				 */
+				aq_free_rxpage(&rxbuf->rxdata,
+					       aq_nic_get_dev(self->aq_nic));
+				self->stats.rx.pg_losts++;
+			}
+		} else {
+			rxbuf->rxdata.pg_off = 0;
+			self->stats.rx.pg_reuses++;
+		}
+	}
+
+	if (!rxbuf->rxdata.page) {
+		ret = aq_get_rxpage(&rxbuf->rxdata, order,
+				    aq_nic_get_dev(self->aq_nic));
+		return ret;
+	}
+
+	return 0;
+}
+
 static struct aq_ring_s *aq_ring_alloc(struct aq_ring_s *self,
 				       struct aq_nic_s *aq_nic)
 {
@@ -81,6 +160,11 @@ struct aq_ring_s *aq_ring_rx_alloc(struct aq_ring_s *self,
 	self->idx = idx;
 	self->size = aq_nic_cfg->rxds;
 	self->dx_size = aq_nic_cfg->aq_hw_caps->rxd_size;
+	self->page_order = fls(AQ_CFG_RX_FRAME_MAX / PAGE_SIZE +
+			       (AQ_CFG_RX_FRAME_MAX % PAGE_SIZE ? 1 : 0)) - 1;
+
+	if (aq_nic_cfg->rxpageorder > self->page_order)
+		self->page_order = aq_nic_cfg->rxpageorder;
 
 	self = aq_ring_alloc(self, aq_nic);
 	if (!self) {
@@ -214,10 +298,8 @@ int aq_ring_rx_clean(struct aq_ring_s *self,
 		unsigned int i = 0U;
 		u16 hdr_len;
 
-		if (buff->is_error) {
-			__free_pages(buff->page, 0);
+		if (buff->is_error)
 			continue;
-		}
 
 		if (buff->is_cleaned)
 			continue;
@@ -247,16 +329,22 @@ int aq_ring_rx_clean(struct aq_ring_s *self,
 			}
 		}
 
+		dma_sync_single_range_for_cpu(aq_nic_get_dev(self->aq_nic),
+					      buff->rxdata.daddr,
+					      buff->rxdata.pg_off,
+					      buff->len, DMA_FROM_DEVICE);
+
 		/* for single fragment packets use build_skb() */
 		if (buff->is_eop &&
 		    buff->len <= AQ_CFG_RX_FRAME_MAX - AQ_SKB_ALIGN) {
-			skb = build_skb(page_address(buff->page),
+			skb = build_skb(aq_buf_vaddr(&buff->rxdata),
 					AQ_CFG_RX_FRAME_MAX);
 			if (unlikely(!skb)) {
 				err = -ENOMEM;
 				goto err_exit;
 			}
 			skb_put(skb, buff->len);
+			page_ref_inc(buff->rxdata.page);
 		} else {
 			skb = napi_alloc_skb(napi, AQ_CFG_RX_HDR_SIZE);
 			if (unlikely(!skb)) {
@@ -266,34 +354,41 @@ int aq_ring_rx_clean(struct aq_ring_s *self,
 
 			hdr_len = buff->len;
 			if (hdr_len > AQ_CFG_RX_HDR_SIZE)
-				hdr_len = eth_get_headlen(page_address(buff->page),
+				hdr_len = eth_get_headlen(aq_buf_vaddr(&buff->rxdata),
 							  AQ_CFG_RX_HDR_SIZE);
 
-			memcpy(__skb_put(skb, hdr_len), page_address(buff->page),
+			memcpy(__skb_put(skb, hdr_len), aq_buf_vaddr(&buff->rxdata),
 			       ALIGN(hdr_len, sizeof(long)));
 
 			if (buff->len - hdr_len > 0) {
-				skb_add_rx_frag(skb, 0, buff->page,
-						hdr_len,
+				skb_add_rx_frag(skb, 0, buff->rxdata.page,
+						buff->rxdata.pg_off + hdr_len,
 						buff->len - hdr_len,
-						SKB_TRUESIZE(buff->len - hdr_len));
+						AQ_CFG_RX_FRAME_MAX);
+				page_ref_inc(buff->rxdata.page);
 			}
 
 			if (!buff->is_eop) {
-				for (i = 1U, next_ = buff->next,
-				     buff_ = &self->buff_ring[next_];
-				     true; next_ = buff_->next,
-				     buff_ = &self->buff_ring[next_], ++i) {
-					skb_add_rx_frag(skb, i,
-							buff_->page, 0,
+				buff_ = buff;
+				i = 1U;
+				do {
+					next_ = buff_->next,
+					buff_ = &self->buff_ring[next_];
+
+					dma_sync_single_range_for_cpu(
+							aq_nic_get_dev(self->aq_nic),
+							buff_->rxdata.daddr,
+							buff_->rxdata.pg_off,
+							buff_->len,
+							DMA_FROM_DEVICE);
+					skb_add_rx_frag(skb, i++,
+							buff_->rxdata.page,
+							buff_->rxdata.pg_off,
 							buff_->len,
-							SKB_TRUESIZE(buff->len -
-							ETH_HLEN));
+							AQ_CFG_RX_FRAME_MAX);
+					page_ref_inc(buff_->rxdata.page);
 					buff_->is_cleaned = 1;
-
-					if (buff_->is_eop)
-						break;
-				}
+				} while (!buff_->is_eop);
 			}
 		}
 
@@ -319,8 +414,7 @@ err_exit:
 
 int aq_ring_rx_fill(struct aq_ring_s *self)
 {
-	unsigned int pages_order = fls(AQ_CFG_RX_FRAME_MAX / PAGE_SIZE +
-		(AQ_CFG_RX_FRAME_MAX % PAGE_SIZE ? 1 : 0)) - 1;
+	unsigned int page_order = self->page_order;
 	struct aq_ring_buff_s *buff = NULL;
 	int err = 0;
 	int i = 0;
@@ -332,30 +426,15 @@ int aq_ring_rx_fill(struct aq_ring_s *self)
 		buff->flags = 0U;
 		buff->len = AQ_CFG_RX_FRAME_MAX;
 
-		buff->page = alloc_pages(GFP_ATOMIC | __GFP_COMP, pages_order);
-		if (!buff->page) {
-			err = -ENOMEM;
+		err = aq_get_rxpages(self, buff, page_order);
+		if (err)
 			goto err_exit;
-		}
-
-		buff->pa = dma_map_page(aq_nic_get_dev(self->aq_nic),
-					buff->page, 0,
-					AQ_CFG_RX_FRAME_MAX, DMA_FROM_DEVICE);
-
-		if (dma_mapping_error(aq_nic_get_dev(self->aq_nic), buff->pa)) {
-			err = -ENOMEM;
-			goto err_exit;
-		}
 
+		buff->pa = aq_buf_daddr(&buff->rxdata);
 		buff = NULL;
 	}
 
 err_exit:
-	if (err < 0) {
-		if (buff && buff->page)
-			__free_pages(buff->page, 0);
-	}
-
 	return err;
 }
 
@@ -368,10 +447,7 @@ void aq_ring_rx_deinit(struct aq_ring_s *self)
 		self->sw_head = aq_ring_next_dx(self, self->sw_head)) {
 		struct aq_ring_buff_s *buff = &self->buff_ring[self->sw_head];
 
-		dma_unmap_page(aq_nic_get_dev(self->aq_nic), buff->pa,
-			       AQ_CFG_RX_FRAME_MAX, DMA_FROM_DEVICE);
-
-		__free_pages(buff->page, 0);
+		aq_free_rxpage(&buff->rxdata, aq_nic_get_dev(self->aq_nic));
 	}
 
 err_exit:;