[dpdk-dev] [PATCH v3] app/testpmd: enable the heavyweight mode TCP/IPv4 GRO

[Jiayu Hu <jiayu.hu@intel.com>]

The GRO library provides two modes to reassemble packets. Currently, the
csum forwarding engine has supported to use the lightweight mode to
reassemble TCP/IPv4 packets. This patch introduces the heavyweight mode
for TCP/IPv4 GRO in the csum forwarding engine.

With the command "set port <port_id> gro on|off", users can enable
TCP/IPv4 GRO for a given port. With the command "set gro flush <cycles>",
users can determine when the GROed TCP/IPv4 packets are flushed from
reassembly tables. With the command "show port <port_id> gro", users can
display GRO configuration.

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
---
changes in v3:
- remove "heavyweight mode" and "lightweight mode" from GRO commands
- combine two patches into one
- use consistent help string for GRO commands 
- remove the unnecessary command "gro set (max_flow_num)
	(max_item_num_per_flow) (port_id)"
changes in v2:
- use "set" and "show" as the root level command
- add a new command to show GRO configuration
- fix l2_len/l3_len/l4_len unset etc. bugs

 app/test-pmd/cmdline.c                      | 206 ++++++++++++++++------------
 app/test-pmd/config.c                       |  67 +++++++--
 app/test-pmd/csumonly.c                     |  31 ++++-
 app/test-pmd/testpmd.c                      |  18 ++-
 app/test-pmd/testpmd.h                      |  16 ++-
 doc/guides/testpmd_app_ug/testpmd_funcs.rst |  45 ++++--
 6 files changed, 263 insertions(+), 120 deletions(-)

diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c
index cd8c358..d628250 100644
--- a/app/test-pmd/cmdline.c
+++ b/app/test-pmd/cmdline.c
@@ -423,13 +423,16 @@ static void cmd_help_long_parsed(void *parsed_result,
 			"tso show (portid)"
 			"    Display the status of TCP Segmentation Offload.\n\n"
 
-			"gro (on|off) (port_id)"
+			"set port (port_id) gro on|off\n"
 			"    Enable or disable Generic Receive Offload in"
 			" csum forwarding engine.\n\n"
 
-			"gro set (max_flow_num) (max_item_num_per_flow) (port_id)\n"
-			"    Set max flow number and max packet number per-flow"
-			" for GRO.\n\n"
+			"show port (port_id) gro\n"
+			"    Display GRO configuration.\n\n"
+
+			"set gro flush (cycles)\n"
+			"    Set the cycle to flush GROed packets from"
+			" reassembly tables.\n\n"
 
 			"set fwd (%s)\n"
 			"    Set packet forwarding mode.\n\n"
@@ -3850,115 +3853,145 @@ cmdline_parse_inst_t cmd_tunnel_tso_show = {
 };
 
 /* *** SET GRO FOR A PORT *** */
-struct cmd_gro_result {
+struct cmd_gro_enable_result {
+	cmdline_fixed_string_t cmd_set;
+	cmdline_fixed_string_t cmd_port;
 	cmdline_fixed_string_t cmd_keyword;
-	cmdline_fixed_string_t mode;
-	uint8_t port_id;
+	cmdline_fixed_string_t cmd_onoff;
+	uint8_t cmd_pid;
 };
 
 static void
-cmd_enable_gro_parsed(void *parsed_result,
+cmd_gro_enable_parsed(void *parsed_result,
 		__attribute__((unused)) struct cmdline *cl,
 		__attribute__((unused)) void *data)
 {
-	struct cmd_gro_result *res;
+	struct cmd_gro_enable_result *res;
 
 	res = parsed_result;
-	setup_gro(res->mode, res->port_id);
-}
-
-cmdline_parse_token_string_t cmd_gro_keyword =
-	TOKEN_STRING_INITIALIZER(struct cmd_gro_result,
+	if (!strcmp(res->cmd_keyword, "gro"))
+		setup_gro(res->cmd_onoff, res->cmd_pid);
+}
+
+cmdline_parse_token_string_t cmd_gro_enable_set =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_enable_result,
+			cmd_set, "set");
+cmdline_parse_token_string_t cmd_gro_enable_port =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_enable_result,
+			cmd_keyword, "port");
+cmdline_parse_token_num_t cmd_gro_enable_pid =
+	TOKEN_NUM_INITIALIZER(struct cmd_gro_enable_result,
+			cmd_pid, UINT8);
+cmdline_parse_token_string_t cmd_gro_enable_keyword =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_enable_result,
 			cmd_keyword, "gro");
-cmdline_parse_token_string_t cmd_gro_mode =
-	TOKEN_STRING_INITIALIZER(struct cmd_gro_result,
-			mode, "on#off");
-cmdline_parse_token_num_t cmd_gro_pid =
-	TOKEN_NUM_INITIALIZER(struct cmd_gro_result,
-			port_id, UINT8);
+cmdline_parse_token_string_t cmd_gro_enable_onoff =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_enable_result,
+			cmd_onoff, "on#off");
 
-cmdline_parse_inst_t cmd_enable_gro = {
-	.f = cmd_enable_gro_parsed,
+cmdline_parse_inst_t cmd_gro_enable = {
+	.f = cmd_gro_enable_parsed,
 	.data = NULL,
-	.help_str = "gro (on|off) (port_id)",
+	.help_str = "set port <port_id> gro on|off",
 	.tokens = {
-		(void *)&cmd_gro_keyword,
-		(void *)&cmd_gro_mode,
-		(void *)&cmd_gro_pid,
+		(void *)&cmd_gro_enable_set,
+		(void *)&cmd_gro_enable_port,
+		(void *)&cmd_gro_enable_pid,
+		(void *)&cmd_gro_enable_keyword,
+		(void *)&cmd_gro_enable_onoff,
 		NULL,
 	},
 };
 
-/* *** SET MAX FLOW NUMBER AND ITEM NUM PER FLOW FOR GRO *** */
-struct cmd_gro_set_result {
-	cmdline_fixed_string_t gro;
-	cmdline_fixed_string_t mode;
-	uint16_t flow_num;
-	uint16_t item_num_per_flow;
-	uint8_t port_id;
+/* *** DISPLAY GRO CONFIGURATION *** */
+struct cmd_gro_show_result {
+	cmdline_fixed_string_t cmd_show;
+	cmdline_fixed_string_t cmd_port;
+	cmdline_fixed_string_t cmd_keyword;
+	uint8_t cmd_pid;
 };
 
 static void
-cmd_gro_set_parsed(void *parsed_result,
-		       __attribute__((unused)) struct cmdline *cl,
-		       __attribute__((unused)) void *data)
+cmd_gro_show_parsed(void *parsed_result,
+		__attribute__((unused)) struct cmdline *cl,
+		__attribute__((unused)) void *data)
 {
-	struct cmd_gro_set_result *res = parsed_result;
+	struct cmd_gro_show_result *res;
 
-	if (port_id_is_invalid(res->port_id, ENABLED_WARN))
-		return;
-	if (test_done == 0) {
-		printf("Before set GRO flow_num and item_num_per_flow,"
-				" please stop forwarding first\n");
-		return;
-	}
+	res = parsed_result;
+	if (!strcmp(res->cmd_keyword, "gro"))
+		show_gro(res->cmd_pid);
+}
+
+cmdline_parse_token_string_t cmd_gro_show_show =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_show_result,
+			cmd_show, "show");
+cmdline_parse_token_string_t cmd_gro_show_port =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_show_result,
+			cmd_port, "port");
+cmdline_parse_token_num_t cmd_gro_show_pid =
+	TOKEN_NUM_INITIALIZER(struct cmd_gro_show_result,
+			cmd_pid, UINT8);
+cmdline_parse_token_string_t cmd_gro_show_keyword =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_show_result,
+			cmd_keyword, "gro");
 
-	if (!strcmp(res->mode, "set")) {
-		if (res->flow_num == 0)
-			printf("Invalid flow number. Revert to default value:"
-					" %u.\n", GRO_DEFAULT_FLOW_NUM);
-		else
-			gro_ports[res->port_id].param.max_flow_num =
-				res->flow_num;
+cmdline_parse_inst_t cmd_gro_show = {
+	.f = cmd_gro_show_parsed,
+	.data = NULL,
+	.help_str = "show port <port_id> gro",
+	.tokens = {
+		(void *)&cmd_gro_show_show,
+		(void *)&cmd_gro_show_port,
+		(void *)&cmd_gro_show_pid,
+		(void *)&cmd_gro_show_keyword,
+		NULL,
+	},
+};
 
-		if (res->item_num_per_flow == 0)
-			printf("Invalid item number per-flow. Revert"
-					" to default value:%u.\n",
-					GRO_DEFAULT_ITEM_NUM_PER_FLOW);
-		else
-			gro_ports[res->port_id].param.max_item_per_flow =
-				res->item_num_per_flow;
-	}
+/* *** SET FLUSH CYCLES FOR GRO *** */
+struct cmd_gro_flush_result {
+	cmdline_fixed_string_t cmd_set;
+	cmdline_fixed_string_t cmd_keyword;
+	cmdline_fixed_string_t cmd_flush;
+	uint8_t cmd_cycles;
+};
+
+static void
+cmd_gro_flush_parsed(void *parsed_result,
+		__attribute__((unused)) struct cmdline *cl,
+		__attribute__((unused)) void *data)
+{
+	struct cmd_gro_flush_result *res;
+
+	res = parsed_result;
+	if ((!strcmp(res->cmd_keyword, "gro")) &&
+			(!strcmp(res->cmd_flush, "flush")))
+		setup_gro_flush_cycles(res->cmd_cycles);
 }
 
-cmdline_parse_token_string_t cmd_gro_set_gro =
-	TOKEN_STRING_INITIALIZER(struct cmd_gro_set_result,
-				gro, "gro");
-cmdline_parse_token_string_t cmd_gro_set_mode =
-	TOKEN_STRING_INITIALIZER(struct cmd_gro_set_result,
-				mode, "set");
-cmdline_parse_token_num_t cmd_gro_set_flow_num =
-	TOKEN_NUM_INITIALIZER(struct cmd_gro_set_result,
-				flow_num, UINT16);
-cmdline_parse_token_num_t cmd_gro_set_item_num_per_flow =
-	TOKEN_NUM_INITIALIZER(struct cmd_gro_set_result,
-				item_num_per_flow, UINT16);
-cmdline_parse_token_num_t cmd_gro_set_portid =
-	TOKEN_NUM_INITIALIZER(struct cmd_gro_set_result,
-				port_id, UINT8);
+cmdline_parse_token_string_t cmd_gro_flush_set =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_flush_result,
+			cmd_set, "set");
+cmdline_parse_token_string_t cmd_gro_flush_keyword =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_flush_result,
+			cmd_keyword, "gro");
+cmdline_parse_token_string_t cmd_gro_flush_flush =
+	TOKEN_STRING_INITIALIZER(struct cmd_gro_flush_result,
+			cmd_flush, "flush");
+cmdline_parse_token_num_t cmd_gro_flush_cycles =
+	TOKEN_NUM_INITIALIZER(struct cmd_gro_flush_result,
+			cmd_cycles, UINT8);
 
-cmdline_parse_inst_t cmd_gro_set = {
-	.f = cmd_gro_set_parsed,
+cmdline_parse_inst_t cmd_gro_flush = {
+	.f = cmd_gro_flush_parsed,
 	.data = NULL,
-	.help_str = "gro set <max_flow_num> <max_item_num_per_flow> "
-		"<port_id>: set max flow number and max packet number per-flow "
-		"for GRO",
+	.help_str = "set gro flush <cycles>",
 	.tokens = {
-		(void *)&cmd_gro_set_gro,
-		(void *)&cmd_gro_set_mode,
-		(void *)&cmd_gro_set_flow_num,
-		(void *)&cmd_gro_set_item_num_per_flow,
-		(void *)&cmd_gro_set_portid,
+		(void *)&cmd_gro_flush_set,
+		(void *)&cmd_gro_flush_keyword,
+		(void *)&cmd_gro_flush_flush,
+		(void *)&cmd_gro_flush_cycles,
 		NULL,
 	},
 };
@@ -14249,8 +14282,9 @@ cmdline_parse_ctx_t main_ctx[] = {
 	(cmdline_parse_inst_t *)&cmd_tso_show,
 	(cmdline_parse_inst_t *)&cmd_tunnel_tso_set,
 	(cmdline_parse_inst_t *)&cmd_tunnel_tso_show,
-	(cmdline_parse_inst_t *)&cmd_enable_gro,
-	(cmdline_parse_inst_t *)&cmd_gro_set,
+	(cmdline_parse_inst_t *)&cmd_gro_enable,
+	(cmdline_parse_inst_t *)&cmd_gro_flush,
+	(cmdline_parse_inst_t *)&cmd_gro_show,
 	(cmdline_parse_inst_t *)&cmd_link_flow_control_set,
 	(cmdline_parse_inst_t *)&cmd_link_flow_control_set_rx,
 	(cmdline_parse_inst_t *)&cmd_link_flow_control_set_tx,
diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
index 3ae3e1c..d97d291 100644
--- a/app/test-pmd/config.c
+++ b/app/test-pmd/config.c
@@ -2420,7 +2420,7 @@ set_tx_pkt_segments(unsigned *seg_lengths, unsigned nb_segs)
 }
 
 void
-setup_gro(const char *mode, uint8_t port_id)
+setup_gro(const char *onoff, uint8_t port_id)
 {
 	if (!rte_eth_dev_is_valid_port(port_id)) {
 		printf("invalid port id %u\n", port_id);
@@ -2431,29 +2431,76 @@ setup_gro(const char *mode, uint8_t port_id)
 				" please stop forwarding first\n");
 		return;
 	}
-	if (strcmp(mode, "on") == 0) {
-		if (gro_ports[port_id].enable) {
-			printf("port %u has enabled GRO\n", port_id);
+	if (strcmp(onoff, "on") == 0) {
+		if (gro_ports[port_id].enable != 0) {
+			printf("Port %u has enabled GRO. Please"
+					" disable GRO first\n", port_id);
 			return;
 		}
-		gro_ports[port_id].enable = 1;
-		gro_ports[port_id].param.gro_types = RTE_GRO_TCP_IPV4;
-
-		if (gro_ports[port_id].param.max_flow_num == 0)
+		if (gro_flush_cycles == GRO_DEFAULT_FLUSH_CYCLES) {
+			gro_ports[port_id].param.gro_types = RTE_GRO_TCP_IPV4;
 			gro_ports[port_id].param.max_flow_num =
 				GRO_DEFAULT_FLOW_NUM;
-		if (gro_ports[port_id].param.max_item_per_flow == 0)
 			gro_ports[port_id].param.max_item_per_flow =
 				GRO_DEFAULT_ITEM_NUM_PER_FLOW;
+		}
+		gro_ports[port_id].enable = 1;
 	} else {
 		if (gro_ports[port_id].enable == 0) {
-			printf("port %u has disabled GRO\n", port_id);
+			printf("Port %u has disabled GRO\n", port_id);
 			return;
 		}
 		gro_ports[port_id].enable = 0;
 	}
 }
 
+void
+setup_gro_flush_cycles(uint8_t cycles)
+{
+	if (test_done == 0) {
+		printf("Before change flush interval for GRO,"
+				" please stop forwarding first\n");
+		return;
+	}
+
+	if (cycles > GRO_MAX_FLUSH_CYCLES) {
+		printf("The flushing cycle be in the range"
+				" of 1 to %u. Revert to the default"
+				" value %u\n",
+				GRO_MAX_FLUSH_CYCLES,
+				GRO_DEFAULT_FLUSH_CYCLES);
+		cycles = GRO_DEFAULT_FLUSH_CYCLES;
+	}
+
+	gro_flush_cycles = cycles;
+}
+
+void
+show_gro(uint8_t port_id)
+{
+	struct rte_gro_param *param;
+	uint32_t max_pkts_num;
+
+	param = &gro_ports[port_id].param;
+
+	if (!rte_eth_dev_is_valid_port(port_id)) {
+		printf("Invalid port id %u\n", port_id);
+		return;
+	}
+	if (gro_ports[port_id].enable) {
+		printf("GRO type: TCP/IPv4\n");
+		if (gro_flush_cycles > 0)
+			max_pkts_num = MAX_PKT_BURST * GRO_MAX_FLUSH_CYCLES;
+		else {
+			max_pkts_num = param->max_flow_num *
+				param->max_item_per_flow;
+		}
+		printf("Max packet number to GRO: %u\n", max_pkts_num);
+		printf("Flushing cycles: %u\n", gro_flush_cycles);
+	} else
+		printf("Port %u doesn't enable GRO\n", port_id);
+}
+
 char*
 list_pkt_forwarding_modes(void)
 {
diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
index 90c8119..ca50ab7 100644
--- a/app/test-pmd/csumonly.c
+++ b/app/test-pmd/csumonly.c
@@ -631,6 +631,9 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
 	struct rte_mbuf *m, *p;
 	struct ether_hdr *eth_hdr;
 	void *l3_hdr = NULL, *outer_l3_hdr = NULL; /* can be IPv4 or IPv6 */
+	void **gro_ctx;
+	uint16_t gro_pkts_num;
+	uint8_t gro_enable;
 	uint16_t nb_rx;
 	uint16_t nb_tx;
 	uint16_t nb_prep;
@@ -657,17 +660,13 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
 				 nb_pkt_per_burst);
 	if (unlikely(nb_rx == 0))
 		return;
-	if (unlikely(gro_ports[fs->rx_port].enable))
-		nb_rx = rte_gro_reassemble_burst(pkts_burst,
-				nb_rx,
-				&(gro_ports[fs->rx_port].param));
-
 #ifdef RTE_TEST_PMD_RECORD_BURST_STATS
 	fs->rx_burst_stats.pkt_burst_spread[nb_rx]++;
 #endif
 	fs->rx_packets += nb_rx;
 	rx_bad_ip_csum = 0;
 	rx_bad_l4_csum = 0;
+	gro_enable = gro_ports[fs->rx_port].enable;
 
 	txp = &ports[fs->tx_port];
 	testpmd_ol_flags = txp->tx_ol_flags;
@@ -851,6 +850,28 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
 		}
 	}
 
+	if (unlikely(gro_enable)) {
+		if (gro_flush_cycles == GRO_DEFAULT_FLUSH_CYCLES) {
+			nb_rx = rte_gro_reassemble_burst(pkts_burst, nb_rx,
+					&(gro_ports[fs->rx_port].param));
+		} else {
+			gro_ctx = current_fwd_lcore()->gro_ctx;
+			nb_rx = rte_gro_reassemble(pkts_burst, nb_rx, gro_ctx);
+
+			if (++fs->gro_times >= gro_flush_cycles) {
+				gro_pkts_num = rte_gro_get_pkt_count(gro_ctx);
+				if (gro_pkts_num > MAX_PKT_BURST - nb_rx)
+					gro_pkts_num = MAX_PKT_BURST - nb_rx;
+
+				nb_rx += rte_gro_timeout_flush(gro_ctx, 0,
+						RTE_GRO_TCP_IPV4,
+						&pkts_burst[nb_rx],
+						gro_pkts_num);
+				fs->gro_times = 0;
+			}
+		}
+	}
+
 	nb_prep = rte_eth_tx_prepare(fs->tx_port, fs->tx_queue,
 			pkts_burst, nb_rx);
 	if (nb_prep != nb_rx)
diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index 7d40139..c1423d5 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -90,7 +90,6 @@
 #ifdef RTE_LIBRTE_LATENCY_STATS
 #include <rte_latencystats.h>
 #endif
-#include <rte_gro.h>
 
 #include "testpmd.h"
 
@@ -386,6 +385,7 @@ uint8_t bitrate_enabled;
 #endif
 
 struct gro_status gro_ports[RTE_MAX_ETHPORTS];
+uint8_t gro_flush_cycles = GRO_DEFAULT_FLUSH_CYCLES;
 
 /* Forward function declarations */
 static void map_port_queue_stats_mapping_registers(uint8_t pi, struct rte_port *port);
@@ -570,6 +570,7 @@ init_config(void)
 	unsigned int nb_mbuf_per_pool;
 	lcoreid_t  lc_id;
 	uint8_t port_per_socket[RTE_MAX_NUMA_NODES];
+	struct rte_gro_param gro_param;
 
 	memset(port_per_socket,0,RTE_MAX_NUMA_NODES);
 
@@ -671,6 +672,20 @@ init_config(void)
 		rte_exit(EXIT_FAILURE, "FAIL from init_fwd_streams()\n");
 
 	fwd_config_setup();
+
+	/* create a gro context for each lcore */
+	gro_param.gro_types = RTE_GRO_TCP_IPV4;
+	gro_param.max_flow_num = GRO_MAX_FLUSH_CYCLES;
+	gro_param.max_item_per_flow = MAX_PKT_BURST;
+	for (lc_id = 0; lc_id < nb_lcores; lc_id++) {
+		gro_param.socket_id = rte_lcore_to_socket_id(
+				fwd_lcores_cpuids[lc_id]);
+		fwd_lcores[lc_id]->gro_ctx = rte_gro_ctx_create(&gro_param);
+		if (fwd_lcores[lc_id]->gro_ctx == NULL) {
+			rte_exit(EXIT_FAILURE,
+					"rte_gro_ctx_create() failed\n");
+		}
+	}
 }
 
 
@@ -1165,6 +1180,7 @@ start_packet_forwarding(int with_tx_first)
 		fwd_streams[sm_id]->fwd_dropped = 0;
 		fwd_streams[sm_id]->rx_bad_ip_csum = 0;
 		fwd_streams[sm_id]->rx_bad_l4_csum = 0;
+		fwd_streams[sm_id]->gro_times = 0;
 
 #ifdef RTE_TEST_PMD_RECORD_BURST_STATS
 		memset(&fwd_streams[sm_id]->rx_burst_stats, 0,
diff --git a/app/test-pmd/testpmd.h b/app/test-pmd/testpmd.h
index c9d7739..e878bcb 100644
--- a/app/test-pmd/testpmd.h
+++ b/app/test-pmd/testpmd.h
@@ -120,6 +120,7 @@ struct fwd_stream {
 	unsigned int fwd_dropped; /**< received packets not forwarded */
 	unsigned int rx_bad_ip_csum ; /**< received packets has bad ip checksum */
 	unsigned int rx_bad_l4_csum ; /**< received packets has bad l4 checksum */
+	unsigned int gro_times;	/**< GRO operation times */
 #ifdef RTE_TEST_PMD_RECORD_CORE_CYCLES
 	uint64_t     core_cycles; /**< used for RX and TX processing */
 #endif
@@ -206,6 +207,7 @@ struct rte_port {
  */
 struct fwd_lcore {
 	struct rte_mempool *mbp; /**< The mbuf pool to use by this core */
+	void *gro_ctx;		/**< GRO context */
 	streamid_t stream_idx;   /**< index of 1st stream in "fwd_streams" */
 	streamid_t stream_nb;    /**< number of streams in "fwd_streams" */
 	lcoreid_t  cpuid_idx;    /**< index of logical core in CPU id table */
@@ -434,13 +436,19 @@ extern struct ether_addr peer_eth_addrs[RTE_MAX_ETHPORTS];
 extern uint32_t burst_tx_delay_time; /**< Burst tx delay time(us) for mac-retry. */
 extern uint32_t burst_tx_retry_num;  /**< Burst tx retry number for mac-retry. */
 
-#define GRO_DEFAULT_FLOW_NUM 4
-#define GRO_DEFAULT_ITEM_NUM_PER_FLOW DEF_PKT_BURST
+#define GRO_DEFAULT_ITEM_NUM_PER_FLOW 32
+#define GRO_DEFAULT_FLOW_NUM (RTE_GRO_MAX_BURST_ITEM_NUM / \
+		GRO_DEFAULT_ITEM_NUM_PER_FLOW)
+
+#define GRO_DEFAULT_FLUSH_CYCLES 1
+#define GRO_MAX_FLUSH_CYCLES 4
+
 struct gro_status {
 	struct rte_gro_param param;
 	uint8_t enable;
 };
 extern struct gro_status gro_ports[RTE_MAX_ETHPORTS];
+extern uint8_t gro_flush_cycles;
 
 static inline unsigned int
 lcore_num(void)
@@ -640,7 +648,9 @@ void get_2tuple_filter(uint8_t port_id, uint16_t index);
 void get_5tuple_filter(uint8_t port_id, uint16_t index);
 int rx_queue_id_is_invalid(queueid_t rxq_id);
 int tx_queue_id_is_invalid(queueid_t txq_id);
-void setup_gro(const char *mode, uint8_t port_id);
+void setup_gro(const char *onoff, uint8_t port_id);
+void setup_gro_flush_cycles(uint8_t cycles);
+void show_gro(uint8_t port_id);
 
 /* Functions to manage the set of filtered Multicast MAC addresses */
 void mcast_addr_add(uint8_t port_id, struct ether_addr *mc_addr);
diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
index 2ed62f5..7f21b7d 100644
--- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
+++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
@@ -898,12 +898,12 @@ Display the status of TCP Segmentation Offload::
 
    testpmd> tso show (port_id)
 
-gro
-~~~
+set port - gro
+~~~~~~~~~~~~~~
 
 Enable or disable GRO in ``csum`` forwarding engine::
 
-   testpmd> gro (on|off) (port_id)
+   testpmd> set port <port_id> gro on|off
 
 If enabled, the csum forwarding engine will perform GRO on the TCP/IPv4
 packets received from the given port.
@@ -914,23 +914,38 @@ GRO. By default, GRO is disabled for all ports.
 .. note::
 
    When enable GRO for a port, TCP/IPv4 packets received from the port
-   will be performed GRO. After GRO, the merged packets are multi-segments.
-   But csum forwarding engine doesn't support to calculate TCP checksum
-   for multi-segment packets in SW. So please select TCP HW checksum
-   calculation for the port which GROed packets are transmitted to.
+   will be performed GRO. After GRO, all merged packets have bad
+   checksums, since the GRO library doesn't re-calculate checksums for
+   the merged packets. Therefore, if users want the merged packets to
+   have correct checksums, please select IP and TCP HW checksum calculation
+   for the port which the merged packets are transmitted to.
 
-gro set
-~~~~~~~
+show port - gro
+~~~~~~~~~~~~~~~
+
+Display GRO configuration for a given port::
+
+   testpmd> show port <port_id> gro
+
+set gro flush
+~~~~~~~~~~~~~
+
+Set the cycle to flush the GROed packets from reassembly tables::
 
-Set max flow number and max packet number per-flow for GRO::
+   testpmd> set gro flush <cycles>
 
-   testpmd> gro set (max_flow_num) (max_item_num_per_flow) (port_id)
+When enable GRO, the csum forwarding engine performs GRO on received
+packets, and the GROed packets are stored in reassembly tables. Users
+can use this command to determine when the GROed packets are flushed
+from the reassembly tables.
 
-The product of ``max_flow_num`` and ``max_item_num_per_flow`` is the max
-number of packets a GRO table can store.
+The ``cycles`` is measured in GRO operation times. The csum forwarding
+engine flushes the GROed packets from the tables every ``cycles`` GRO
+operations.
 
-If current packet number is greater than or equal to the max value, GRO
-will stop processing incoming packets.
+By default, the value of ``cycles`` is 1, which means flush GROed packets
+from the reassembly tables as soon as one GRO operation finishes. The value
+of ``cycles`` should be in the range of 1 to ``GRO_MAX_FLUSH_CYCLES``.
 
 mac_addr add
 ~~~~~~~~~~~~
-- 
2.7.4