[net-next 01/11] igb: push data into first igb_tx_buffer sooner to reduce stack usage

[Jeff Kirsher <jeffrey.t.kirsher@intel.com>]

From: Alexander Duyck <alexander.h.duyck@intel.com>

Instead of storing most of the data for the TX hot path in the stack until
we are ready to write the descriptor we can save ourselves some time and
effort by pushing the SKB, tx_flags, gso_size, bytecount, and protocol into
the first igb_tx_buffer since that is where we will end up putting it
anyway.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by:  Aaron Brown  <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---
 drivers/net/ethernet/intel/igb/igb.h      |    1 +
 drivers/net/ethernet/intel/igb/igb_main.c |  103 +++++++++++++++--------------
 2 files changed, 54 insertions(+), 50 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 77793a9..de35c02 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -146,6 +146,7 @@ struct igb_tx_buffer {
 	struct sk_buff *skb;
 	unsigned int bytecount;
 	u16 gso_segs;
+	__be16 protocol;
 	dma_addr_t dma;
 	u32 length;
 	u32 tx_flags;
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 862dd7c..1c234f0 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3975,10 +3975,11 @@ void igb_tx_ctxtdesc(struct igb_ring *tx_ring, u32 vlan_macip_lens,
 	context_desc->mss_l4len_idx	= cpu_to_le32(mss_l4len_idx);
 }
 
-static inline int igb_tso(struct igb_ring *tx_ring, struct sk_buff *skb,
-			  u32 tx_flags, __be16 protocol, u8 *hdr_len)
+static int igb_tso(struct igb_ring *tx_ring,
+		   struct igb_tx_buffer *first,
+		   u8 *hdr_len)
 {
-	int err;
+	struct sk_buff *skb = first->skb;
 	u32 vlan_macip_lens, type_tucmd;
 	u32 mss_l4len_idx, l4len;
 
@@ -3986,7 +3987,7 @@ static inline int igb_tso(struct igb_ring *tx_ring, struct sk_buff *skb,
 		return 0;
 
 	if (skb_header_cloned(skb)) {
-		err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
+		int err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
 		if (err)
 			return err;
 	}
@@ -3994,7 +3995,7 @@ static inline int igb_tso(struct igb_ring *tx_ring, struct sk_buff *skb,
 	/* ADV DTYP TUCMD MKRLOC/ISCSIHEDLEN */
 	type_tucmd = E1000_ADVTXD_TUCMD_L4T_TCP;
 
-	if (protocol == __constant_htons(ETH_P_IP)) {
+	if (first->protocol == __constant_htons(ETH_P_IP)) {
 		struct iphdr *iph = ip_hdr(skb);
 		iph->tot_len = 0;
 		iph->check = 0;
@@ -4003,16 +4004,26 @@ static inline int igb_tso(struct igb_ring *tx_ring, struct sk_buff *skb,
 							 IPPROTO_TCP,
 							 0);
 		type_tucmd |= E1000_ADVTXD_TUCMD_IPV4;
+		first->tx_flags |= IGB_TX_FLAGS_TSO |
+				   IGB_TX_FLAGS_CSUM |
+				   IGB_TX_FLAGS_IPV4;
 	} else if (skb_is_gso_v6(skb)) {
 		ipv6_hdr(skb)->payload_len = 0;
 		tcp_hdr(skb)->check = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 						       &ipv6_hdr(skb)->daddr,
 						       0, IPPROTO_TCP, 0);
+		first->tx_flags |= IGB_TX_FLAGS_TSO |
+				   IGB_TX_FLAGS_CSUM;
 	}
 
+	/* compute header lengths */
 	l4len = tcp_hdrlen(skb);
 	*hdr_len = skb_transport_offset(skb) + l4len;
 
+	/* update gso size and bytecount with header size */
+	first->gso_segs = skb_shinfo(skb)->gso_segs;
+	first->bytecount += (first->gso_segs - 1) * *hdr_len;
+
 	/* MSS L4LEN IDX */
 	mss_l4len_idx = l4len << E1000_ADVTXD_L4LEN_SHIFT;
 	mss_l4len_idx |= skb_shinfo(skb)->gso_size << E1000_ADVTXD_MSS_SHIFT;
@@ -4020,26 +4031,26 @@ static inline int igb_tso(struct igb_ring *tx_ring, struct sk_buff *skb,
 	/* VLAN MACLEN IPLEN */
 	vlan_macip_lens = skb_network_header_len(skb);
 	vlan_macip_lens |= skb_network_offset(skb) << E1000_ADVTXD_MACLEN_SHIFT;
-	vlan_macip_lens |= tx_flags & IGB_TX_FLAGS_VLAN_MASK;
+	vlan_macip_lens |= first->tx_flags & IGB_TX_FLAGS_VLAN_MASK;
 
 	igb_tx_ctxtdesc(tx_ring, vlan_macip_lens, type_tucmd, mss_l4len_idx);
 
 	return 1;
 }
 
-static inline bool igb_tx_csum(struct igb_ring *tx_ring, struct sk_buff *skb,
-			       u32 tx_flags, __be16 protocol)
+static void igb_tx_csum(struct igb_ring *tx_ring, struct igb_tx_buffer *first)
 {
+	struct sk_buff *skb = first->skb;
 	u32 vlan_macip_lens = 0;
 	u32 mss_l4len_idx = 0;
 	u32 type_tucmd = 0;
 
 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
-		if (!(tx_flags & IGB_TX_FLAGS_VLAN))
-			return false;
+		if (!(first->tx_flags & IGB_TX_FLAGS_VLAN))
+			return;
 	} else {
 		u8 l4_hdr = 0;
-		switch (protocol) {
+		switch (first->protocol) {
 		case __constant_htons(ETH_P_IP):
 			vlan_macip_lens |= skb_network_header_len(skb);
 			type_tucmd |= E1000_ADVTXD_TUCMD_IPV4;
@@ -4053,7 +4064,7 @@ static inline bool igb_tx_csum(struct igb_ring *tx_ring, struct sk_buff *skb,
 			if (unlikely(net_ratelimit())) {
 				dev_warn(tx_ring->dev,
 				 "partial checksum but proto=%x!\n",
-				 protocol);
+				 first->protocol);
 			}
 			break;
 		}
@@ -4081,14 +4092,15 @@ static inline bool igb_tx_csum(struct igb_ring *tx_ring, struct sk_buff *skb,
 			}
 			break;
 		}
+
+		/* update TX checksum flag */
+		first->tx_flags |= IGB_TX_FLAGS_CSUM;
 	}
 
 	vlan_macip_lens |= skb_network_offset(skb) << E1000_ADVTXD_MACLEN_SHIFT;
-	vlan_macip_lens |= tx_flags & IGB_TX_FLAGS_VLAN_MASK;
+	vlan_macip_lens |= first->tx_flags & IGB_TX_FLAGS_VLAN_MASK;
 
 	igb_tx_ctxtdesc(tx_ring, vlan_macip_lens, type_tucmd, mss_l4len_idx);
-
-	return (skb->ip_summed == CHECKSUM_PARTIAL);
 }
 
 static __le32 igb_tx_cmd_type(u32 tx_flags)
@@ -4113,8 +4125,9 @@ static __le32 igb_tx_cmd_type(u32 tx_flags)
 	return cmd_type;
 }
 
-static __le32 igb_tx_olinfo_status(u32 tx_flags, unsigned int paylen,
-				   struct igb_ring *tx_ring)
+static void igb_tx_olinfo_status(struct igb_ring *tx_ring,
+				 union e1000_adv_tx_desc *tx_desc,
+				 u32 tx_flags, unsigned int paylen)
 {
 	u32 olinfo_status = paylen << E1000_ADVTXD_PAYLEN_SHIFT;
 
@@ -4132,7 +4145,7 @@ static __le32 igb_tx_olinfo_status(u32 tx_flags, unsigned int paylen,
 			olinfo_status |= E1000_TXD_POPTS_IXSM << 8;
 	}
 
-	return cpu_to_le32(olinfo_status);
+	tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
 }
 
 /*
@@ -4140,12 +4153,13 @@ static __le32 igb_tx_olinfo_status(u32 tx_flags, unsigned int paylen,
  * maintain a power of two alignment we have to limit ourselves to 32K.
  */
 #define IGB_MAX_TXD_PWR	15
-#define IGB_MAX_DATA_PER_TXD	(1 << IGB_MAX_TXD_PWR)
+#define IGB_MAX_DATA_PER_TXD	(1<<IGB_MAX_TXD_PWR)
 
-static void igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
-		       struct igb_tx_buffer *first, u32 tx_flags,
+static void igb_tx_map(struct igb_ring *tx_ring,
+		       struct igb_tx_buffer *first,
 		       const u8 hdr_len)
 {
+	struct sk_buff *skb = first->skb;
 	struct igb_tx_buffer *tx_buffer_info;
 	union e1000_adv_tx_desc *tx_desc;
 	dma_addr_t dma;
@@ -4154,24 +4168,12 @@ static void igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
 	unsigned int size = skb_headlen(skb);
 	unsigned int paylen = skb->len - hdr_len;
 	__le32 cmd_type;
+	u32 tx_flags = first->tx_flags;
 	u16 i = tx_ring->next_to_use;
-	u16 gso_segs;
-
-	if (tx_flags & IGB_TX_FLAGS_TSO)
-		gso_segs = skb_shinfo(skb)->gso_segs;
-	else
-		gso_segs = 1;
-
-	/* multiply data chunks by size of headers */
-	first->bytecount = paylen + (gso_segs * hdr_len);
-	first->gso_segs = gso_segs;
-	first->skb = skb;
 
 	tx_desc = IGB_TX_DESC(tx_ring, i);
 
-	tx_desc->read.olinfo_status =
-		igb_tx_olinfo_status(tx_flags, paylen, tx_ring);
-
+	igb_tx_olinfo_status(tx_ring, tx_desc, tx_flags, paylen);
 	cmd_type = igb_tx_cmd_type(tx_flags);
 
 	dma = dma_map_single(tx_ring->dev, skb->data, size, DMA_TO_DEVICE);
@@ -4181,7 +4183,6 @@ static void igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
 	/* record length, and DMA address */
 	first->length = size;
 	first->dma = dma;
-	first->tx_flags = tx_flags;
 	tx_desc->read.buffer_addr = cpu_to_le64(dma);
 
 	for (;;) {
@@ -4336,6 +4337,12 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 		return NETDEV_TX_BUSY;
 	}
 
+	/* record the location of the first descriptor for this packet */
+	first = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
+	first->skb = skb;
+	first->bytecount = skb->len;
+	first->gso_segs = 1;
+
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
 		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 		tx_flags |= IGB_TX_FLAGS_TSTAMP;
@@ -4346,22 +4353,17 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 		tx_flags |= (vlan_tx_tag_get(skb) << IGB_TX_FLAGS_VLAN_SHIFT);
 	}
 
-	/* record the location of the first descriptor for this packet */
-	first = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
+	/* record initial flags and protocol */
+	first->tx_flags = tx_flags;
+	first->protocol = protocol;
 
-	tso = igb_tso(tx_ring, skb, tx_flags, protocol, &hdr_len);
-	if (tso < 0) {
+	tso = igb_tso(tx_ring, first, &hdr_len);
+	if (tso < 0)
 		goto out_drop;
-	} else if (tso) {
-		tx_flags |= IGB_TX_FLAGS_TSO | IGB_TX_FLAGS_CSUM;
-		if (protocol == htons(ETH_P_IP))
-			tx_flags |= IGB_TX_FLAGS_IPV4;
-	} else if (igb_tx_csum(tx_ring, skb, tx_flags, protocol) &&
-		   (skb->ip_summed == CHECKSUM_PARTIAL)) {
-		tx_flags |= IGB_TX_FLAGS_CSUM;
-	}
+	else if (!tso)
+		igb_tx_csum(tx_ring, first);
 
-	igb_tx_map(tx_ring, skb, first, tx_flags, hdr_len);
+	igb_tx_map(tx_ring, first, hdr_len);
 
 	/* Make sure there is space in the ring for the next send. */
 	igb_maybe_stop_tx(tx_ring, MAX_SKB_FRAGS + 4);
@@ -4369,7 +4371,8 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 
 out_drop:
-	dev_kfree_skb_any(skb);
+	igb_unmap_and_free_tx_resource(tx_ring, first);
+
 	return NETDEV_TX_OK;
 }
 
-- 
1.7.6.4