enic: Add support for adaptive interrupt coalescing

This patch adds support for adaptive interrupt coalescing.

For small pkts with low pkt rate, we can decrease the coalescing interrupt
dynamically which decreases the latency. This however increases the cpu
utilization. Based on testing with different coal intr and pkt rate we came up
with a table(mod_table) with rx_rate and coalescing interrupt value where we
get low latency without significant increase in cpu. mod_table table stores
the coalescing timer percentage value for different throughputs.

Function enic_calc_int_moderation() calculates the desired coalescing intr timer
value. This function is called in driver rx napi_poll. The actual value is set
by enic_set_int_moderation() which is called when napi_poll is complete. i.e
when we unmask the rx intr.

Adaptive coal intr is support only when driver is using msix intr. Because
intr is not shared.

Struct mod_range is used to store only the default adaptive coalescing intr
value.

Adaptive coal intr calue is calculated by

timer = range_start + ((rx_coal->range_end - range_start) *
		       mod_table[index].range_percent / 100);

rx_coal->range_end is the rx-usecs-high value set using ethtool.
range_start is rx-usecs-low, set using ethtool, if rx_small_pkt_bytes_cnt is
greater than 2 * rx_large_pkt_bytes_cnt. i.e small pkts are dominant. Else its
rx-usecs-low + 3.

Cc: Christian Benvenuti <benve@cisco.com>
Cc: Neel Patel <neepatel@cisco.com>
Signed-off-by: Sujith Sankar <ssujith@cisco.com>
Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 55 insertions, 6 deletions

diff --git a/drivers/net/ethernet/cisco/enic/enic_ethtool.c b/drivers/net/ethernet/cisco/enic/enic_ethtool.c
index 58a8c67638e..1882db230e1 100644
--- a/drivers/net/ethernet/cisco/enic/enic_ethtool.c
+++ b/drivers/net/ethernet/cisco/enic/enic_ethtool.c
@@ -79,6 +79,17 @@ static const struct enic_stat enic_rx_stats[] = {
 static const unsigned int enic_n_tx_stats = ARRAY_SIZE(enic_tx_stats);
 static const unsigned int enic_n_rx_stats = ARRAY_SIZE(enic_rx_stats);
 
+void enic_intr_coal_set_rx(struct enic *enic, u32 timer)
+{
+	int i;
+	int intr;
+
+	for (i = 0; i < enic->rq_count; i++) {
+		intr = enic_msix_rq_intr(enic, i);
+		vnic_intr_coalescing_timer_set(&enic->intr[intr], timer);
+	}
+}
+
 static int enic_get_settings(struct net_device *netdev,
 	struct ethtool_cmd *ecmd)
 {
@@ -178,9 +189,14 @@ static int enic_get_coalesce(struct net_device *netdev,
 	struct ethtool_coalesce *ecmd)
 {
 	struct enic *enic = netdev_priv(netdev);
+	struct enic_rx_coal *rxcoal = &enic->rx_coalesce_setting;
 
 	ecmd->tx_coalesce_usecs = enic->tx_coalesce_usecs;
 	ecmd->rx_coalesce_usecs = enic->rx_coalesce_usecs;
+	if (rxcoal->use_adaptive_rx_coalesce)
+		ecmd->use_adaptive_rx_coalesce = 1;
+	ecmd->rx_coalesce_usecs_low = rxcoal->small_pkt_range_start;
+	ecmd->rx_coalesce_usecs_high = rxcoal->range_end;
 
 	return 0;
 }
@@ -191,17 +207,31 @@ static int enic_set_coalesce(struct net_device *netdev,
 	struct enic *enic = netdev_priv(netdev);
 	u32 tx_coalesce_usecs;
 	u32 rx_coalesce_usecs;
+	u32 rx_coalesce_usecs_low;
+	u32 rx_coalesce_usecs_high;
+	u32 coalesce_usecs_max;
 	unsigned int i, intr;
+	struct enic_rx_coal *rxcoal = &enic->rx_coalesce_setting;
 
+	coalesce_usecs_max = vnic_dev_get_intr_coal_timer_max(enic->vdev);
 	tx_coalesce_usecs = min_t(u32, ecmd->tx_coalesce_usecs,
-		vnic_dev_get_intr_coal_timer_max(enic->vdev));
+				  coalesce_usecs_max);
 	rx_coalesce_usecs = min_t(u32, ecmd->rx_coalesce_usecs,
-		vnic_dev_get_intr_coal_timer_max(enic->vdev));
+				  coalesce_usecs_max);
+
+	rx_coalesce_usecs_low = min_t(u32, ecmd->rx_coalesce_usecs_low,
+				      coalesce_usecs_max);
+	rx_coalesce_usecs_high = min_t(u32, ecmd->rx_coalesce_usecs_high,
+				       coalesce_usecs_max);
 
 	switch (vnic_dev_get_intr_mode(enic->vdev)) {
 	case VNIC_DEV_INTR_MODE_INTX:
 		if (tx_coalesce_usecs != rx_coalesce_usecs)
 			return -EINVAL;
+		if (ecmd->use_adaptive_rx_coalesce	||
+		    ecmd->rx_coalesce_usecs_low		||
+		    ecmd->rx_coalesce_usecs_high)
+			return -EOPNOTSUPP;
 
 		intr = enic_legacy_io_intr();
 		vnic_intr_coalescing_timer_set(&enic->intr[intr],
@@ -210,6 +240,10 @@ static int enic_set_coalesce(struct net_device *netdev,
 	case VNIC_DEV_INTR_MODE_MSI:
 		if (tx_coalesce_usecs != rx_coalesce_usecs)
 			return -EINVAL;
+		if (ecmd->use_adaptive_rx_coalesce	||
+		    ecmd->rx_coalesce_usecs_low		||
+		    ecmd->rx_coalesce_usecs_high)
+			return -EOPNOTSUPP;
 
 		vnic_intr_coalescing_timer_set(&enic->intr[0],
 			tx_coalesce_usecs);
@@ -221,12 +255,27 @@ static int enic_set_coalesce(struct net_device *netdev,
 				tx_coalesce_usecs);
 		}
 
-		for (i = 0; i < enic->rq_count; i++) {
-			intr = enic_msix_rq_intr(enic, i);
-			vnic_intr_coalescing_timer_set(&enic->intr[intr],
-				rx_coalesce_usecs);
+		if (rxcoal->use_adaptive_rx_coalesce) {
+			if (!ecmd->use_adaptive_rx_coalesce) {
+				rxcoal->use_adaptive_rx_coalesce = 0;
+				enic_intr_coal_set_rx(enic, rx_coalesce_usecs);
+			}
+		} else {
+			if (ecmd->use_adaptive_rx_coalesce)
+				rxcoal->use_adaptive_rx_coalesce = 1;
+			else
+				enic_intr_coal_set_rx(enic, rx_coalesce_usecs);
 		}
 
+		if (ecmd->rx_coalesce_usecs_high) {
+			if (rx_coalesce_usecs_high <
+			    (rx_coalesce_usecs_low + ENIC_AIC_LARGE_PKT_DIFF))
+				return -EINVAL;
+			rxcoal->range_end = rx_coalesce_usecs_high;
+			rxcoal->small_pkt_range_start = rx_coalesce_usecs_low;
+			rxcoal->large_pkt_range_start = rx_coalesce_usecs_low +
+							ENIC_AIC_LARGE_PKT_DIFF;
+		}
 		break;
 	default:
 		break;