Thread (9 messages) flat view 9 messages, 2 authors, 2019-11-15
STALE2457d

Revision v2 of 2 in this series.

Revisions (2)
  1. v1 [diff vs current]
  2. v2 current

[PATCH v2 net-next 6/7] net: stmmac: Rework TX Coalesce logic

From: Jose Abreu <Jose.Abreu@synopsys.com>
Date: 2019-11-14 11:43:27
Also in: lkml, netdev
Subsystem: networking drivers, stmmac ethernet driver, the rest · Maintainers: Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Maxime Chevallier, Linus Torvalds 

Coalesce logic currently increments the number of packets and sets the
IC bit when the coalesced packets have passed a given limit. This does
not reflect very well what coalesce was meant for as we can have a large
number of packets that are coalesced and then a single one, sent later
on that has the IC bit.

Rework the logic so that it coalesces only upon a limit of packets and
sets the IC bit for large number of packets.

Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>

---
Cc: Giuseppe Cavallaro <redacted>
Cc: Alexandre Torgue <redacted>
Cc: Jose Abreu <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: netdev@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 61 ++++++++++++++++-------
 1 file changed, 42 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 400fbb727fd5..4ba250a9008f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2916,16 +2916,17 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct stmmac_priv *priv = netdev_priv(dev);
 	int nfrags = skb_shinfo(skb)->nr_frags;
 	u32 queue = skb_get_queue_mapping(skb);
+	unsigned int first_entry, tx_packets;
+	int tmp_pay_len = 0, first_tx;
 	struct stmmac_tx_queue *tx_q;
-	unsigned int first_entry;
 	u8 proto_hdr_len, hdr;
-	int tmp_pay_len = 0;
+	bool has_vlan, set_ic;
 	u32 pay_len, mss;
 	dma_addr_t des;
-	bool has_vlan;
 	int i;
 
 	tx_q = &priv->tx_queue[queue];
+	first_tx = tx_q->cur_tx;
 
 	/* Compute header lengths */
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
@@ -3033,16 +3034,27 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 	tx_q->tx_skbuff[tx_q->cur_tx] = skb;
 
 	/* Manage tx mitigation */
-	tx_q->tx_count_frames += nfrags + 1;
-	if (likely(priv->tx_coal_frames > tx_q->tx_count_frames) &&
-	    !((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) &&
-	      priv->hwts_tx_en)) {
-		stmmac_tx_timer_arm(priv, queue);
-	} else {
+	tx_packets = (tx_q->cur_tx + 1) - first_tx;
+	tx_q->tx_count_frames += tx_packets;
+
+	if ((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) && priv->hwts_tx_en)
+		set_ic = true;
+	else if (!priv->tx_coal_frames)
+		set_ic = false;
+	else if (tx_packets > priv->tx_coal_frames)
+		set_ic = true;
+	else if ((tx_q->tx_count_frames % priv->tx_coal_frames) < tx_packets)
+		set_ic = true;
+	else
+		set_ic = false;
+
+	if (set_ic) {
 		desc = &tx_q->dma_tx[tx_q->cur_tx];
 		tx_q->tx_count_frames = 0;
 		stmmac_set_tx_ic(priv, desc);
 		priv->xstats.tx_set_ic_bit++;
+	} else {
+		stmmac_tx_timer_arm(priv, queue);
 	}
 
 	/* We've used all descriptors we need for this skb, however,
@@ -3133,6 +3145,7 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
  */
 static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 {
+	unsigned int first_entry, tx_packets, enh_desc;
 	struct stmmac_priv *priv = netdev_priv(dev);
 	unsigned int nopaged_len = skb_headlen(skb);
 	int i, csum_insertion = 0, is_jumbo = 0;
@@ -3141,13 +3154,12 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	int gso = skb_shinfo(skb)->gso_type;
 	struct dma_desc *desc, *first;
 	struct stmmac_tx_queue *tx_q;
-	unsigned int first_entry;
-	unsigned int enh_desc;
+	bool has_vlan, set_ic;
+	int entry, first_tx;
 	dma_addr_t des;
-	bool has_vlan;
-	int entry;
 
 	tx_q = &priv->tx_queue[queue];
+	first_tx = tx_q->cur_tx;
 
 	if (priv->tx_path_in_lpi_mode)
 		stmmac_disable_eee_mode(priv);
@@ -3241,12 +3253,21 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	 * This approach takes care about the fragments: desc is the first
 	 * element in case of no SG.
 	 */
-	tx_q->tx_count_frames += nfrags + 1;
-	if (likely(priv->tx_coal_frames > tx_q->tx_count_frames) &&
-	    !((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) &&
-	      priv->hwts_tx_en)) {
-		stmmac_tx_timer_arm(priv, queue);
-	} else {
+	tx_packets = (entry + 1) - first_tx;
+	tx_q->tx_count_frames += tx_packets;
+
+	if ((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) && priv->hwts_tx_en)
+		set_ic = true;
+	else if (!priv->tx_coal_frames)
+		set_ic = false;
+	else if (tx_packets > priv->tx_coal_frames)
+		set_ic = true;
+	else if ((tx_q->tx_count_frames % priv->tx_coal_frames) < tx_packets)
+		set_ic = true;
+	else
+		set_ic = false;
+
+	if (set_ic) {
 		if (likely(priv->extend_desc))
 			desc = &tx_q->dma_etx[entry].basic;
 		else
@@ -3255,6 +3276,8 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 		tx_q->tx_count_frames = 0;
 		stmmac_set_tx_ic(priv, desc);
 		priv->xstats.tx_set_ic_bit++;
+	} else {
+		stmmac_tx_timer_arm(priv, queue);
 	}
 
 	/* We've used all descriptors we need for this skb, however,
-- 
2.7.4


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