[PATCH net-next V1 3/4] net/dim: Support adaptive TX moderation

[Tal Gilboa <talgi@mellanox.com>]

Interrupt moderation for TX traffic requires different profiles than RX
interrupt moderation. The main goal here is to reduce interrupt rate and
allow better payload aggregation by keeping SKBs in the TX queue a bit
longer. Ping-pong behavior would get a profile with a short timer, so
latency wouldn't increase for these scenarios. There's a slight degradtion
in bandwidth for single stream with large message sizes, since
net.ipv4.tcp_limit_output_bytes is limiting the allowed TX traffic, but
with many streams performance is always improved.

Performance improvements (ConnectX-5 100GbE)
Bandwidth: increased up to 40% (1024B with 10s of streams).
Interrupt rate: reduced up to 50% (1024B with 1000s of streams).

Performance degradation (ConnectX-5 100GbE)
Bandwidth: up to 10% decrease single stream TCP (1MB message size from
51Gb/s to 47Gb/s).

*Both cases with TX EQE based moderation enabled.

Signed-off-by: Tal Gilboa <talgi@mellanox.com>
---
 include/linux/net_dim.h | 64 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 51 insertions(+), 13 deletions(-)

diff --git a/include/linux/net_dim.h b/include/linux/net_dim.h
index d34fbfe..9449a61 100644
--- a/include/linux/net_dim.h
+++ b/include/linux/net_dim.h
@@ -104,11 +104,12 @@ enum {
 #define NET_DIM_PARAMS_NUM_PROFILES 5
 /* Adaptive moderation profiles */
 #define NET_DIM_DEFAULT_RX_CQ_MODERATION_PKTS_FROM_EQE 256
+#define NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE 128
 #define NET_DIM_DEF_PROFILE_CQE 1
 #define NET_DIM_DEF_PROFILE_EQE 1
 
 /* All profiles sizes must be NET_PARAMS_DIM_NUM_PROFILES */
-#define NET_DIM_EQE_PROFILES { \
+#define NET_DIM_RX_EQE_PROFILES { \
 	{1,   NET_DIM_DEFAULT_RX_CQ_MODERATION_PKTS_FROM_EQE}, \
 	{8,   NET_DIM_DEFAULT_RX_CQ_MODERATION_PKTS_FROM_EQE}, \
 	{64,  NET_DIM_DEFAULT_RX_CQ_MODERATION_PKTS_FROM_EQE}, \
@@ -116,7 +117,7 @@ enum {
 	{256, NET_DIM_DEFAULT_RX_CQ_MODERATION_PKTS_FROM_EQE}, \
 }
 
-#define NET_DIM_CQE_PROFILES { \
+#define NET_DIM_RX_CQE_PROFILES { \
 	{2,  256},             \
 	{8,  128},             \
 	{16, 64},              \
@@ -124,16 +125,38 @@ enum {
 	{64, 64}               \
 }
 
+#define NET_DIM_TX_EQE_PROFILES { \
+	{1,   NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE},  \
+	{8,   NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE},  \
+	{32,  NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE},  \
+	{64,  NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE},  \
+	{128, NET_DIM_DEFAULT_TX_CQ_MODERATION_PKTS_FROM_EQE}   \
+}
+
+#define NET_DIM_TX_CQE_PROFILES { \
+	{5,  128},  \
+	{8,  64},  \
+	{16, 32},  \
+	{32, 32},  \
+	{64, 32}   \
+}
+
+static const struct net_dim_cq_moder
+rx_profile[NET_DIM_CQ_PERIOD_NUM_MODES][NET_DIM_PARAMS_NUM_PROFILES] = {
+	NET_DIM_RX_EQE_PROFILES,
+	NET_DIM_RX_CQE_PROFILES,
+};
+
 static const struct net_dim_cq_moder
-profile[NET_DIM_CQ_PERIOD_NUM_MODES][NET_DIM_PARAMS_NUM_PROFILES] = {
-	NET_DIM_EQE_PROFILES,
-	NET_DIM_CQE_PROFILES,
+tx_profile[NET_DIM_CQ_PERIOD_NUM_MODES][NET_DIM_PARAMS_NUM_PROFILES] = {
+	NET_DIM_TX_EQE_PROFILES,
+	NET_DIM_TX_CQE_PROFILES,
 };
 
 static inline struct net_dim_cq_moder
 net_dim_get_rx_moderation(u8 cq_period_mode, int ix)
 {
-	struct net_dim_cq_moder cq_moder = profile[cq_period_mode][ix];
+	struct net_dim_cq_moder cq_moder = rx_profile[cq_period_mode][ix];
 
 	cq_moder.cq_period_mode = cq_period_mode;
 	cq_moder.enabled = true;
@@ -141,16 +164,31 @@ enum {
 }
 
 static inline struct net_dim_cq_moder
-net_dim_get_def_rx_moderation(u8 rx_cq_period_mode)
+net_dim_get_def_rx_moderation(u8 cq_period_mode)
 {
-	int default_profile_ix;
+	u8 profile_ix = cq_period_mode == NET_DIM_CQ_PERIOD_MODE_START_FROM_CQE ?
+			NET_DIM_DEF_PROFILE_CQE : NET_DIM_DEF_PROFILE_EQE;
 
-	if (rx_cq_period_mode == NET_DIM_CQ_PERIOD_MODE_START_FROM_CQE)
-		default_profile_ix = NET_DIM_DEF_PROFILE_CQE;
-	else /* NET_DIM_CQ_PERIOD_MODE_START_FROM_EQE */
-		default_profile_ix = NET_DIM_DEF_PROFILE_EQE;
+	return net_dim_get_rx_moderation(cq_period_mode, profile_ix);
+}
+
+static inline struct net_dim_cq_moder
+net_dim_get_tx_moderation(u8 cq_period_mode, int ix)
+{
+	struct net_dim_cq_moder cq_moder = tx_profile[cq_period_mode][ix];
+
+	cq_moder.cq_period_mode = cq_period_mode;
+	cq_moder.enabled = true;
+	return cq_moder;
+}
+
+static inline struct net_dim_cq_moder
+net_dim_get_def_tx_moderation(u8 cq_period_mode)
+{
+	u8 profile_ix = cq_period_mode == NET_DIM_CQ_PERIOD_MODE_START_FROM_CQE ?
+			NET_DIM_DEF_PROFILE_CQE : NET_DIM_DEF_PROFILE_EQE;
 
-	return net_dim_get_rx_moderation(rx_cq_period_mode, default_profile_ix);
+	return net_dim_get_tx_moderation(cq_period_mode, profile_ix);
 }
 
 static inline bool net_dim_on_top(struct net_dim *dim)
-- 
1.8.3.1