Date:   Sat, 11 Feb 2017 21:30:19 -0800
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Scott Peterson <scott.d.peterson@...el.com>,
        netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
        jogreene@...hat.com, Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 05/14] i40e/i40evf: eliminate i40e_pull_tail()

From: Scott Peterson <scott.d.peterson@...el.com>

Reorganize the i40e_pull_tail() logic, doing it in i40e_add_rx_frag()
where it's cheaper.  The igb driver does this the same way.

Also renames i40e_page_is_reserved() to reflect what it actually
tests.

Change-ID: Icd9cc507aae1fcdc02308b3a09034111b4c24071
Signed-off-by: Scott Peterson <scott.d.peterson@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   | 169 ++++++++++++++------------
 drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 169 ++++++++++++++------------
 2 files changed, 186 insertions(+), 152 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index aa9755b..1202b4c7 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1426,45 +1426,6 @@ void i40e_process_skb_fields(struct i40e_ring *rx_ring,
 }
 
 /**
- * i40e_pull_tail - i40e specific version of skb_pull_tail
- * @rx_ring: rx descriptor ring packet is being transacted on
- * @skb: pointer to current skb being adjusted
- *
- * This function is an i40e specific version of __pskb_pull_tail.  The
- * main difference between this version and the original function is that
- * this function can make several assumptions about the state of things
- * that allow for significant optimizations versus the standard function.
- * As a result we can do things like drop a frag and maintain an accurate
- * truesize for the skb.
- */
-static void i40e_pull_tail(struct i40e_ring *rx_ring, struct sk_buff *skb)
-{
-	struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
-	unsigned char *va;
-	unsigned int pull_len;
-
-	/* it is valid to use page_address instead of kmap since we are
-	 * working with pages allocated out of the lomem pool per
-	 * alloc_page(GFP_ATOMIC)
-	 */
-	va = skb_frag_address(frag);
-
-	/* we need the header to contain the greater of either ETH_HLEN or
-	 * 60 bytes if the skb->len is less than 60 for skb_pad.
-	 */
-	pull_len = eth_get_headlen(va, I40E_RX_HDR_SIZE);
-
-	/* align pull length to size of long to optimize memcpy performance */
-	skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
-
-	/* update all of the pointers */
-	skb_frag_size_sub(frag, pull_len);
-	frag->page_offset += pull_len;
-	skb->data_len -= pull_len;
-	skb->tail += pull_len;
-}
-
-/**
  * i40e_cleanup_headers - Correct empty headers
  * @rx_ring: rx descriptor ring packet is being transacted on
  * @skb: pointer to current skb being fixed
@@ -1479,10 +1440,6 @@ static void i40e_pull_tail(struct i40e_ring *rx_ring, struct sk_buff *skb)
  **/
 static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb)
 {
-	/* place header in linear portion of buffer */
-	if (skb_is_nonlinear(skb))
-		i40e_pull_tail(rx_ring, skb);
-
 	/* if eth_skb_pad returns an error the skb was freed */
 	if (eth_skb_pad(skb))
 		return true;
@@ -1514,12 +1471,78 @@ static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
 }
 
 /**
- * i40e_page_is_reserved - check if reuse is possible
+ * i40e_page_is_reusable - check if any reuse is possible
  * @page: page struct to check
+ *
+ * A page is not reusable if it was allocated under low memory
+ * conditions, or it's not in the same NUMA node as this CPU.
  */
-static inline bool i40e_page_is_reserved(struct page *page)
+static inline bool i40e_page_is_reusable(struct page *page)
 {
-	return (page_to_nid(page) != numa_mem_id()) || page_is_pfmemalloc(page);
+	return (page_to_nid(page) == numa_mem_id()) &&
+		!page_is_pfmemalloc(page);
+}
+
+/**
+ * i40e_can_reuse_rx_page - Determine if this page can be reused by
+ * the adapter for another receive
+ *
+ * @rx_buffer: buffer containing the page
+ * @page: page address from rx_buffer
+ * @truesize: actual size of the buffer in this page
+ *
+ * If page is reusable, rx_buffer->page_offset is adjusted to point to
+ * an unused region in the page.
+ *
+ * For small pages, @truesize will be a constant value, half the size
+ * of the memory at page.  We'll attempt to alternate between high and
+ * low halves of the page, with one half ready for use by the hardware
+ * and the other half being consumed by the stack.  We use the page
+ * ref count to determine whether the stack has finished consuming the
+ * portion of this page that was passed up with a previous packet.  If
+ * the page ref count is >1, we'll assume the "other" half page is
+ * still busy, and this page cannot be reused.
+ *
+ * For larger pages, @truesize will be the actual space used by the
+ * received packet (adjusted upward to an even multiple of the cache
+ * line size).  This will advance through the page by the amount
+ * actually consumed by the received packets while there is still
+ * space for a buffer.  Each region of larger pages will be used at
+ * most once, after which the page will not be reused.
+ *
+ * In either case, if the page is reusable its refcount is increased.
+ **/
+static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
+				   struct page *page,
+				   const unsigned int truesize)
+{
+#if (PAGE_SIZE >= 8192)
+	unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
+#endif
+
+	/* Is any reuse possible? */
+	if (unlikely(!i40e_page_is_reusable(page)))
+		return false;
+
+#if (PAGE_SIZE < 8192)
+	/* if we are only owner of page we can reuse it */
+	if (unlikely(page_count(page) != 1))
+		return false;
+
+	/* flip page offset to other buffer */
+	rx_buffer->page_offset ^= truesize;
+#else
+	/* move offset up to the next cache line */
+	rx_buffer->page_offset += truesize;
+
+	if (rx_buffer->page_offset > last_offset)
+		return false;
+#endif
+
+	/* Inc ref count on page before passing it up to the stack */
+	get_page(page);
+
+	return true;
 }
 
 /**
@@ -1543,23 +1566,25 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
 			     struct sk_buff *skb)
 {
 	struct page *page = rx_buffer->page;
+	unsigned char *va = page_address(page) + rx_buffer->page_offset;
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = I40E_RXBUFFER_2048;
 #else
 	unsigned int truesize = ALIGN(size, L1_CACHE_BYTES);
-	unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
 #endif
+	unsigned int pull_len;
+
+	if (unlikely(skb_is_nonlinear(skb)))
+		goto add_tail_frag;
 
 	/* will the data fit in the skb we allocated? if so, just
 	 * copy it as it is pretty small anyway
 	 */
-	if ((size <= I40E_RX_HDR_SIZE) && !skb_is_nonlinear(skb)) {
-		unsigned char *va = page_address(page) + rx_buffer->page_offset;
-
+	if (size <= I40E_RX_HDR_SIZE) {
 		memcpy(__skb_put(skb, size), va, ALIGN(size, sizeof(long)));
 
-		/* page is not reserved, we can reuse buffer as-is */
-		if (likely(!i40e_page_is_reserved(page)))
+		/* page is reusable, we can reuse buffer as-is */
+		if (likely(i40e_page_is_reusable(page)))
 			return true;
 
 		/* this page cannot be reused so discard it */
@@ -1567,34 +1592,26 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
 		return false;
 	}
 
-	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
-			rx_buffer->page_offset, size, truesize);
-
-	/* avoid re-using remote pages */
-	if (unlikely(i40e_page_is_reserved(page)))
-		return false;
-
-#if (PAGE_SIZE < 8192)
-	/* if we are only owner of page we can reuse it */
-	if (unlikely(page_count(page) != 1))
-		return false;
+	/* we need the header to contain the greater of either
+	 * ETH_HLEN or 60 bytes if the skb->len is less than
+	 * 60 for skb_pad.
+	 */
+	pull_len = eth_get_headlen(va, I40E_RX_HDR_SIZE);
 
-	/* flip page offset to other buffer */
-	rx_buffer->page_offset ^= truesize;
-#else
-	/* move offset up to the next cache line */
-	rx_buffer->page_offset += truesize;
+	/* align pull length to size of long to optimize
+	 * memcpy performance
+	 */
+	memcpy(__skb_put(skb, pull_len), va, ALIGN(pull_len, sizeof(long)));
 
-	if (rx_buffer->page_offset > last_offset)
-		return false;
-#endif
+	/* update all of the pointers */
+	va += pull_len;
+	size -= pull_len;
 
-	/* Even if we own the page, we are not allowed to use atomic_set()
-	 * This would break get_page_unless_zero() users.
-	 */
-	get_page(rx_buffer->page);
+add_tail_frag:
+	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
+			(unsigned long)va & ~PAGE_MASK, size, truesize);
 
-	return true;
+	return i40e_can_reuse_rx_page(rx_buffer, page, truesize);
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 7e9c425..b758846 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -904,45 +904,6 @@ void i40evf_process_skb_fields(struct i40e_ring *rx_ring,
 }
 
 /**
- * i40e_pull_tail - i40e specific version of skb_pull_tail
- * @rx_ring: rx descriptor ring packet is being transacted on
- * @skb: pointer to current skb being adjusted
- *
- * This function is an i40e specific version of __pskb_pull_tail.  The
- * main difference between this version and the original function is that
- * this function can make several assumptions about the state of things
- * that allow for significant optimizations versus the standard function.
- * As a result we can do things like drop a frag and maintain an accurate
- * truesize for the skb.
- */
-static void i40e_pull_tail(struct i40e_ring *rx_ring, struct sk_buff *skb)
-{
-	struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
-	unsigned char *va;
-	unsigned int pull_len;
-
-	/* it is valid to use page_address instead of kmap since we are
-	 * working with pages allocated out of the lomem pool per
-	 * alloc_page(GFP_ATOMIC)
-	 */
-	va = skb_frag_address(frag);
-
-	/* we need the header to contain the greater of either ETH_HLEN or
-	 * 60 bytes if the skb->len is less than 60 for skb_pad.
-	 */
-	pull_len = eth_get_headlen(va, I40E_RX_HDR_SIZE);
-
-	/* align pull length to size of long to optimize memcpy performance */
-	skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
-
-	/* update all of the pointers */
-	skb_frag_size_sub(frag, pull_len);
-	frag->page_offset += pull_len;
-	skb->data_len -= pull_len;
-	skb->tail += pull_len;
-}
-
-/**
  * i40e_cleanup_headers - Correct empty headers
  * @rx_ring: rx descriptor ring packet is being transacted on
  * @skb: pointer to current skb being fixed
@@ -957,10 +918,6 @@ static void i40e_pull_tail(struct i40e_ring *rx_ring, struct sk_buff *skb)
  **/
 static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb)
 {
-	/* place header in linear portion of buffer */
-	if (skb_is_nonlinear(skb))
-		i40e_pull_tail(rx_ring, skb);
-
 	/* if eth_skb_pad returns an error the skb was freed */
 	if (eth_skb_pad(skb))
 		return true;
@@ -992,12 +949,78 @@ static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
 }
 
 /**
- * i40e_page_is_reserved - check if reuse is possible
+ * i40e_page_is_reusable - check if any reuse is possible
  * @page: page struct to check
+ *
+ * A page is not reusable if it was allocated under low memory
+ * conditions, or it's not in the same NUMA node as this CPU.
  */
-static inline bool i40e_page_is_reserved(struct page *page)
+static inline bool i40e_page_is_reusable(struct page *page)
 {
-	return (page_to_nid(page) != numa_mem_id()) || page_is_pfmemalloc(page);
+	return (page_to_nid(page) == numa_mem_id()) &&
+		!page_is_pfmemalloc(page);
+}
+
+/**
+ * i40e_can_reuse_rx_page - Determine if this page can be reused by
+ * the adapter for another receive
+ *
+ * @rx_buffer: buffer containing the page
+ * @page: page address from rx_buffer
+ * @truesize: actual size of the buffer in this page
+ *
+ * If page is reusable, rx_buffer->page_offset is adjusted to point to
+ * an unused region in the page.
+ *
+ * For small pages, @truesize will be a constant value, half the size
+ * of the memory at page.  We'll attempt to alternate between high and
+ * low halves of the page, with one half ready for use by the hardware
+ * and the other half being consumed by the stack.  We use the page
+ * ref count to determine whether the stack has finished consuming the
+ * portion of this page that was passed up with a previous packet.  If
+ * the page ref count is >1, we'll assume the "other" half page is
+ * still busy, and this page cannot be reused.
+ *
+ * For larger pages, @truesize will be the actual space used by the
+ * received packet (adjusted upward to an even multiple of the cache
+ * line size).  This will advance through the page by the amount
+ * actually consumed by the received packets while there is still
+ * space for a buffer.  Each region of larger pages will be used at
+ * most once, after which the page will not be reused.
+ *
+ * In either case, if the page is reusable its refcount is increased.
+ **/
+static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
+				   struct page *page,
+				   const unsigned int truesize)
+{
+#if (PAGE_SIZE >= 8192)
+	unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
+#endif
+
+	/* Is any reuse possible? */
+	if (unlikely(!i40e_page_is_reusable(page)))
+		return false;
+
+#if (PAGE_SIZE < 8192)
+	/* if we are only owner of page we can reuse it */
+	if (unlikely(page_count(page) != 1))
+		return false;
+
+	/* flip page offset to other buffer */
+	rx_buffer->page_offset ^= truesize;
+#else
+	/* move offset up to the next cache line */
+	rx_buffer->page_offset += truesize;
+
+	if (rx_buffer->page_offset > last_offset)
+		return false;
+#endif
+
+	/* Inc ref count on page before passing it up to the stack */
+	get_page(page);
+
+	return true;
 }
 
 /**
@@ -1021,23 +1044,25 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
 			     struct sk_buff *skb)
 {
 	struct page *page = rx_buffer->page;
+	unsigned char *va = page_address(page) + rx_buffer->page_offset;
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = I40E_RXBUFFER_2048;
 #else
 	unsigned int truesize = ALIGN(size, L1_CACHE_BYTES);
-	unsigned int last_offset = PAGE_SIZE - I40E_RXBUFFER_2048;
 #endif
+	unsigned int pull_len;
+
+	if (unlikely(skb_is_nonlinear(skb)))
+		goto add_tail_frag;
 
 	/* will the data fit in the skb we allocated? if so, just
 	 * copy it as it is pretty small anyway
 	 */
-	if ((size <= I40E_RX_HDR_SIZE) && !skb_is_nonlinear(skb)) {
-		unsigned char *va = page_address(page) + rx_buffer->page_offset;
-
+	if (size <= I40E_RX_HDR_SIZE) {
 		memcpy(__skb_put(skb, size), va, ALIGN(size, sizeof(long)));
 
-		/* page is not reserved, we can reuse buffer as-is */
-		if (likely(!i40e_page_is_reserved(page)))
+		/* page is reusable, we can reuse buffer as-is */
+		if (likely(i40e_page_is_reusable(page)))
 			return true;
 
 		/* this page cannot be reused so discard it */
@@ -1045,34 +1070,26 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring,
 		return false;
 	}
 
-	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
-			rx_buffer->page_offset, size, truesize);
-
-	/* avoid re-using remote pages */
-	if (unlikely(i40e_page_is_reserved(page)))
-		return false;
-
-#if (PAGE_SIZE < 8192)
-	/* if we are only owner of page we can reuse it */
-	if (unlikely(page_count(page) != 1))
-		return false;
+	/* we need the header to contain the greater of either
+	 * ETH_HLEN or 60 bytes if the skb->len is less than
+	 * 60 for skb_pad.
+	 */
+	pull_len = eth_get_headlen(va, I40E_RX_HDR_SIZE);
 
-	/* flip page offset to other buffer */
-	rx_buffer->page_offset ^= truesize;
-#else
-	/* move offset up to the next cache line */
-	rx_buffer->page_offset += truesize;
+	/* align pull length to size of long to optimize
+	 * memcpy performance
+	 */
+	memcpy(__skb_put(skb, pull_len), va, ALIGN(pull_len, sizeof(long)));
 
-	if (rx_buffer->page_offset > last_offset)
-		return false;
-#endif
+	/* update all of the pointers */
+	va += pull_len;
+	size -= pull_len;
 
-	/* Even if we own the page, we are not allowed to use atomic_set()
-	 * This would break get_page_unless_zero() users.
-	 */
-	get_page(rx_buffer->page);
+add_tail_frag:
+	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page,
+			(unsigned long)va & ~PAGE_MASK, size, truesize);
 
-	return true;
+	return i40e_can_reuse_rx_page(rx_buffer, page, truesize);
 }
 
 /**
-- 
2.10.2

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