[v2] examples/l3fwd: add option to set Tx burst size

Message ID 20241204020622.977156-1-haijie1@huawei.com (mailing list archive)
State New
Delegated to: Thomas Monjalon
Headers
Series [v2] examples/l3fwd: add option to set Tx burst size |

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Commit Message

Jie Hai Dec. 4, 2024, 2:06 a.m. UTC
The application send packets only when the buffer is full, or the
buffer is empty and the packets to be sent extends TX_PKT_BURST.
The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
increase, while the default cache size is 256. The packets in
the TX direction occupy the cache. As a result, the performance
deteriorates.

Restore the default Tx burst and add option '--tx-burst' to set
the Tx burst size. To ensure consistency, rename the option
'--burst' to '--rx-burst'. The valid range of the user-provided
value is (0, MAX_PKT_BURST] for both directions.

Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
Cc: stable@dpdk.org

Signed-off-by: Jie Hai <haijie1@huawei.com>
---
 examples/l3fwd/l3fwd.h        | 14 +++---
 examples/l3fwd/l3fwd_acl.c    |  2 +-
 examples/l3fwd/l3fwd_common.h |  2 +-
 examples/l3fwd/l3fwd_em.c     |  2 +-
 examples/l3fwd/l3fwd_fib.c    |  2 +-
 examples/l3fwd/l3fwd_lpm.c    |  2 +-
 examples/l3fwd/main.c         | 89 ++++++++++++++++++-----------------
 7 files changed, 59 insertions(+), 54 deletions(-)
  

Comments

Jie Hai Feb. 14, 2025, 2:11 a.m. UTC | #1
Hi, all maintainers,

Kindly ping for review.

Thanks,
Jie Hai

On 2024/12/4 10:06, Jie Hai wrote:
> The application send packets only when the buffer is full, or the
> buffer is empty and the packets to be sent extends TX_PKT_BURST.
> The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
> increase, while the default cache size is 256. The packets in
> the TX direction occupy the cache. As a result, the performance
> deteriorates.
> 
> Restore the default Tx burst and add option '--tx-burst' to set
> the Tx burst size. To ensure consistency, rename the option
> '--burst' to '--rx-burst'. The valid range of the user-provided
> value is (0, MAX_PKT_BURST] for both directions.
> 
> Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Jie Hai <haijie1@huawei.com>
> ---
>   examples/l3fwd/l3fwd.h        | 14 +++---
>   examples/l3fwd/l3fwd_acl.c    |  2 +-
>   examples/l3fwd/l3fwd_common.h |  2 +-
>   examples/l3fwd/l3fwd_em.c     |  2 +-
>   examples/l3fwd/l3fwd_fib.c    |  2 +-
>   examples/l3fwd/l3fwd_lpm.c    |  2 +-
>   examples/l3fwd/main.c         | 89 ++++++++++++++++++-----------------
>   7 files changed, 59 insertions(+), 54 deletions(-)
> 
> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
> index 0cce3406ee7d..a4e23b817edf 100644
> --- a/examples/l3fwd/l3fwd.h
> +++ b/examples/l3fwd/l3fwd.h
> @@ -32,10 +32,6 @@
>   
>   #define VECTOR_SIZE_DEFAULT   MAX_PKT_BURST
>   #define VECTOR_TMO_NS_DEFAULT 1E6 /* 1ms */
> -/*
> - * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
> - */
> -#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
>   
>   #define NB_SOCKETS        8
>   
> @@ -116,7 +112,11 @@ extern struct acl_algorithms acl_alg[];
>   
>   extern uint32_t max_pkt_len;
>   
> -extern uint32_t nb_pkt_per_burst;
> +extern uint32_t rx_pkt_burst;
> +/*
> + * Try to avoid TX buffering if we have at least tx_pkt_burst packets to send.
> + */
> +extern uint32_t tx_pkt_burst;
>   extern uint32_t mb_mempool_cache_size;
>   
>   /* Send burst of packets on an output interface */
> @@ -152,8 +152,8 @@ send_single_packet(struct lcore_conf *qconf,
>   	len++;
>   
>   	/* enough pkts to be sent */
> -	if (unlikely(len == MAX_PKT_BURST)) {
> -		send_burst(qconf, MAX_PKT_BURST, port);
> +	if (unlikely(len == tx_pkt_burst)) {
> +		send_burst(qconf, tx_pkt_burst, port);
>   		len = 0;
>   	}
>   
> diff --git a/examples/l3fwd/l3fwd_acl.c b/examples/l3fwd/l3fwd_acl.c
> index 4fc4b986cce6..a5af82357a03 100644
> --- a/examples/l3fwd/l3fwd_acl.c
> +++ b/examples/l3fwd/l3fwd_acl.c
> @@ -1136,7 +1136,7 @@ acl_main_loop(__rte_unused void *dummy)
>   			portid = qconf->rx_queue_list[i].port_id;
>   			queueid = qconf->rx_queue_list[i].queue_id;
>   			nb_rx = rte_eth_rx_burst(portid, queueid,
> -				pkts_burst, nb_pkt_per_burst);
> +				pkts_burst, rx_pkt_burst);
>   
>   			if (nb_rx > 0) {
>   				nb_drop = acl_process_pkts(pkts_burst, hops,
> diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
> index d94e5f135791..34fe70b9415c 100644
> --- a/examples/l3fwd/l3fwd_common.h
> +++ b/examples/l3fwd/l3fwd_common.h
> @@ -71,7 +71,7 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
>   	 * If TX buffer for that queue is empty, and we have enough packets,
>   	 * then send them straightway.
>   	 */
> -	if (num >= MAX_TX_BURST && len == 0) {
> +	if (num >= tx_pkt_burst / 2 && len == 0) {
>   		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
>   		if (unlikely(n < num)) {
>   			do {
> diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
> index da9c45e3a482..ea74506ed971 100644
> --- a/examples/l3fwd/l3fwd_em.c
> +++ b/examples/l3fwd/l3fwd_em.c
> @@ -644,7 +644,7 @@ em_main_loop(__rte_unused void *dummy)
>   			portid = qconf->rx_queue_list[i].port_id;
>   			queueid = qconf->rx_queue_list[i].queue_id;
>   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> -				nb_pkt_per_burst);
> +				rx_pkt_burst);
>   			if (nb_rx == 0)
>   				continue;
>   
> diff --git a/examples/l3fwd/l3fwd_fib.c b/examples/l3fwd/l3fwd_fib.c
> index 82f1739df778..4223540b30ae 100644
> --- a/examples/l3fwd/l3fwd_fib.c
> +++ b/examples/l3fwd/l3fwd_fib.c
> @@ -239,7 +239,7 @@ fib_main_loop(__rte_unused void *dummy)
>   			portid = qconf->rx_queue_list[i].port_id;
>   			queueid = qconf->rx_queue_list[i].queue_id;
>   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> -					nb_pkt_per_burst);
> +					rx_pkt_burst);
>   			if (nb_rx == 0)
>   				continue;
>   
> diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
> index fec0aeb79c6a..bd1307c43e70 100644
> --- a/examples/l3fwd/l3fwd_lpm.c
> +++ b/examples/l3fwd/l3fwd_lpm.c
> @@ -205,7 +205,7 @@ lpm_main_loop(__rte_unused void *dummy)
>   			portid = qconf->rx_queue_list[i].port_id;
>   			queueid = qconf->rx_queue_list[i].queue_id;
>   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> -				nb_pkt_per_burst);
> +				rx_pkt_burst);
>   			if (nb_rx == 0)
>   				continue;
>   
> diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
> index 994b7dd8e596..48453faf7c56 100644
> --- a/examples/l3fwd/main.c
> +++ b/examples/l3fwd/main.c
> @@ -57,7 +57,8 @@
>   static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST, "MAX_PKT_BURST should be at most MEMPOOL_CACHE_SIZE");
>   uint16_t nb_rxd = RX_DESC_DEFAULT;
>   uint16_t nb_txd = TX_DESC_DEFAULT;
> -uint32_t nb_pkt_per_burst = DEFAULT_PKT_BURST;
> +uint32_t rx_pkt_burst = DEFAULT_PKT_BURST;
> +uint32_t tx_pkt_burst = DEFAULT_PKT_BURST;
>   uint32_t mb_mempool_cache_size = MEMPOOL_CACHE_SIZE;
>   
>   /**< Ports set in promiscuous mode off by default. */
> @@ -399,7 +400,8 @@ print_usage(const char *prgname)
>   		" --config (port,queue,lcore)[,(port,queue,lcore)]"
>   		" [--rx-queue-size NPKTS]"
>   		" [--tx-queue-size NPKTS]"
> -		" [--burst NPKTS]"
> +		" [--rx-burst NPKTS]"
> +		" [--tx-burst NPKTS]"
>   		" [--mbcache CACHESZ]"
>   		" [--eth-dest=X,MM:MM:MM:MM:MM:MM]"
>   		" [--max-pkt-len PKTLEN]"
> @@ -426,8 +428,10 @@ print_usage(const char *prgname)
>   		"            Default: %d\n"
>   		"  --tx-queue-size NPKTS: Tx queue size in decimal\n"
>   		"            Default: %d\n"
> -		"  --burst NPKTS: Burst size in decimal\n"
> -		"            Default: %d\n"
> +		"  --rx-burst NPKTS: RX Burst size in decimal\n"
> +		"            Default: %d, Maximum: %d\n"
> +		"  --tx-burst NPKTS: TX Burst size in decimal\n"
> +		"            Default: %d, Maximum: %d\n"
>   		"  --mbcache CACHESZ: Mbuf cache size in decimal\n"
>   		"            Default: %d\n"
>   		"  --eth-dest=X,MM:MM:MM:MM:MM:MM: Ethernet destination for port X\n"
> @@ -459,7 +463,10 @@ print_usage(const char *prgname)
>   		"                    another is route entry at while line leads with character '%c'.\n"
>   		"  --rule_ipv6=FILE: Specify the ipv6 rules entries file.\n"
>   		"  --alg: ACL classify method to use, one of: %s.\n\n",
> -		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT, DEFAULT_PKT_BURST, MEMPOOL_CACHE_SIZE,
> +		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT,
> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> +		MEMPOOL_CACHE_SIZE,
>   		ACL_LEAD_CHAR, ROUTE_LEAD_CHAR, alg);
>   }
>   
> @@ -693,47 +700,30 @@ parse_mbcache_size(const char *optarg)
>   			 RTE_MEMPOOL_CACHE_MAX_SIZE);
>   }
>   
> -static void
> -parse_pkt_burst(const char *optarg)
> +static int
> +parse_pkt_burst(const char *optarg, bool is_rx)
>   {
> -	struct rte_eth_dev_info dev_info;
>   	unsigned long pkt_burst;
> -	uint16_t burst_size;
>   	char *end = NULL;
> -	int ret;
>   
>   	/* parse decimal string */
>   	pkt_burst = strtoul(optarg, &end, 10);
> -	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0'))
> -		return;
> -
> -	if (pkt_burst > MAX_PKT_BURST) {
> -		RTE_LOG(INFO, L3FWD, "User provided burst must be <= %d. Using default value %d\n",
> -			MAX_PKT_BURST, nb_pkt_per_burst);
> -		return;
> -	} else if (pkt_burst > 0) {
> -		nb_pkt_per_burst = (uint32_t)pkt_burst;
> -		return;
> +	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0')) {
> +		RTE_LOG(ERR, L3FWD, "Invalid %s-burst\n", is_rx ? "rx" : "tx");
> +		return -1;
>   	}
>   
> -	/* If user gives a value of zero, query the PMD for its recommended Rx burst size. */
> -	ret = rte_eth_dev_info_get(0, &dev_info);
> -	if (ret != 0)
> -		return;
> -	burst_size = dev_info.default_rxportconf.burst_size;
> -	if (burst_size == 0) {
> -		RTE_LOG(INFO, L3FWD, "PMD does not recommend a burst size. Using default value %d. "
> -			"User provided value must be in [1, %d]\n",
> -			nb_pkt_per_burst, MAX_PKT_BURST);
> -		return;
> -	} else if (burst_size > MAX_PKT_BURST) {
> -		RTE_LOG(INFO, L3FWD, "PMD recommended burst size %d exceeds maximum value %d. "
> -			"Using default value %d\n",
> -			burst_size, MAX_PKT_BURST, nb_pkt_per_burst);
> -		return;
> +	if (pkt_burst > MAX_PKT_BURST || pkt_burst == 0) {
> +		RTE_LOG(ERR, L3FWD, "User-provided %s burst must be in (0, %d].\n",
> +			is_rx ? "Rx" : "Tx", MAX_PKT_BURST);
> +		return -1;
> +	} else if (pkt_burst > 0) {
> +		if (is_rx)
> +			rx_pkt_burst = (uint16_t)pkt_burst;
> +		else
> +			tx_pkt_burst = (uint16_t)pkt_burst;
>   	}
> -	nb_pkt_per_burst = burst_size;
> -	RTE_LOG(INFO, L3FWD, "Using PMD-provided burst value %d\n", burst_size);
> +	return 0;
>   }
>   
>   #define MAX_JUMBO_PKT_LEN  9600
> @@ -767,7 +757,8 @@ static const char short_options[] =
>   #define CMD_LINE_OPT_RULE_IPV4 "rule_ipv4"
>   #define CMD_LINE_OPT_RULE_IPV6 "rule_ipv6"
>   #define CMD_LINE_OPT_ALG "alg"
> -#define CMD_LINE_OPT_PKT_BURST "burst"
> +#define CMD_LINE_OPT_PKT_RX_BURST "rx-burst"
> +#define CMD_LINE_OPT_PKT_TX_BURST "tx-burst"
>   #define CMD_LINE_OPT_MB_CACHE_SIZE "mbcache"
>   
>   enum {
> @@ -798,7 +789,8 @@ enum {
>   	CMD_LINE_OPT_ENABLE_VECTOR_NUM,
>   	CMD_LINE_OPT_VECTOR_SIZE_NUM,
>   	CMD_LINE_OPT_VECTOR_TMO_NS_NUM,
> -	CMD_LINE_OPT_PKT_BURST_NUM,
> +	CMD_LINE_OPT_RX_PKT_BURST_NUM,
> +	CMD_LINE_OPT_TX_PKT_BURST_NUM,
>   	CMD_LINE_OPT_MB_CACHE_SIZE_NUM,
>   };
>   
> @@ -826,7 +818,8 @@ static const struct option lgopts[] = {
>   	{CMD_LINE_OPT_RULE_IPV4,   1, 0, CMD_LINE_OPT_RULE_IPV4_NUM},
>   	{CMD_LINE_OPT_RULE_IPV6,   1, 0, CMD_LINE_OPT_RULE_IPV6_NUM},
>   	{CMD_LINE_OPT_ALG,   1, 0, CMD_LINE_OPT_ALG_NUM},
> -	{CMD_LINE_OPT_PKT_BURST,   1, 0, CMD_LINE_OPT_PKT_BURST_NUM},
> +	{CMD_LINE_OPT_PKT_RX_BURST,   1, 0, CMD_LINE_OPT_RX_PKT_BURST_NUM},
> +	{CMD_LINE_OPT_PKT_TX_BURST,   1, 0, CMD_LINE_OPT_TX_PKT_BURST_NUM},
>   	{CMD_LINE_OPT_MB_CACHE_SIZE,   1, 0, CMD_LINE_OPT_MB_CACHE_SIZE_NUM},
>   	{NULL, 0, 0, 0}
>   };
> @@ -916,8 +909,20 @@ parse_args(int argc, char **argv)
>   			parse_queue_size(optarg, &nb_txd, 0);
>   			break;
>   
> -		case CMD_LINE_OPT_PKT_BURST_NUM:
> -			parse_pkt_burst(optarg);
> +		case CMD_LINE_OPT_TX_PKT_BURST_NUM:
> +			ret = parse_pkt_burst(optarg, false);
> +			if (ret) {
> +				print_usage(prgname);
> +				return -1;
> +			}
> +			break;
> +
> +		case CMD_LINE_OPT_RX_PKT_BURST_NUM:
> +			ret = parse_pkt_burst(optarg, true);
> +			if (ret) {
> +				print_usage(prgname);
> +				return -1;
> +			}
>   			break;
>   
>   		case CMD_LINE_OPT_MB_CACHE_SIZE_NUM:
  
fengchengwen Feb. 14, 2025, 8:35 a.m. UTC | #2
Acked-by: Chengwen Feng <fengchengwen@huawei.com>

On 2024/12/4 10:06, Jie Hai wrote:
> The application send packets only when the buffer is full, or the
> buffer is empty and the packets to be sent extends TX_PKT_BURST.
> The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
> increase, while the default cache size is 256. The packets in
> the TX direction occupy the cache. As a result, the performance
> deteriorates.
> 
> Restore the default Tx burst and add option '--tx-burst' to set
> the Tx burst size. To ensure consistency, rename the option
> '--burst' to '--rx-burst'. The valid range of the user-provided
> value is (0, MAX_PKT_BURST] for both directions.
> 
> Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Jie Hai <haijie1@huawei.com>
  
Konstantin Ananyev Feb. 19, 2025, 5:01 p.m. UTC | #3
> On 2024/12/4 10:06, Jie Hai wrote:
> > The application send packets only when the buffer is full, or the
> > buffer is empty and the packets to be sent extends TX_PKT_BURST.
> > The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
> > increase, while the default cache size is 256. The packets in
> > the TX direction occupy the cache. As a result, the performance
> > deteriorates.
> >
> > Restore the default Tx burst and add option '--tx-burst' to set
> > the Tx burst size. To ensure consistency, rename the option
> > '--burst' to '--rx-burst'. The valid range of the user-provided
> > value is (0, MAX_PKT_BURST] for both directions.
> >
> > Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
> > Cc: stable@dpdk.org

Wouldn't that patch:
https://patchwork.dpdk.org/project/dpdk/patch/20250212045416.2393001-1-sivaprasad.tummala@amd.com/
fix that issue too?
And probably in a less disruptive manner?

> > Signed-off-by: Jie Hai <haijie1@huawei.com>
> > ---
> >   examples/l3fwd/l3fwd.h        | 14 +++---
> >   examples/l3fwd/l3fwd_acl.c    |  2 +-
> >   examples/l3fwd/l3fwd_common.h |  2 +-
> >   examples/l3fwd/l3fwd_em.c     |  2 +-
> >   examples/l3fwd/l3fwd_fib.c    |  2 +-
> >   examples/l3fwd/l3fwd_lpm.c    |  2 +-
> >   examples/l3fwd/main.c         | 89 ++++++++++++++++++-----------------
> >   7 files changed, 59 insertions(+), 54 deletions(-)
> >
> > diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
> > index 0cce3406ee7d..a4e23b817edf 100644
> > --- a/examples/l3fwd/l3fwd.h
> > +++ b/examples/l3fwd/l3fwd.h
> > @@ -32,10 +32,6 @@
> >
> >   #define VECTOR_SIZE_DEFAULT   MAX_PKT_BURST
> >   #define VECTOR_TMO_NS_DEFAULT 1E6 /* 1ms */
> > -/*
> > - * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
> > - */
> > -#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
> >
> >   #define NB_SOCKETS        8
> >
> > @@ -116,7 +112,11 @@ extern struct acl_algorithms acl_alg[];
> >
> >   extern uint32_t max_pkt_len;
> >
> > -extern uint32_t nb_pkt_per_burst;
> > +extern uint32_t rx_pkt_burst;
> > +/*
> > + * Try to avoid TX buffering if we have at least tx_pkt_burst packets to send.
> > + */
> > +extern uint32_t tx_pkt_burst;
> >   extern uint32_t mb_mempool_cache_size;
> >
> >   /* Send burst of packets on an output interface */
> > @@ -152,8 +152,8 @@ send_single_packet(struct lcore_conf *qconf,
> >   	len++;
> >
> >   	/* enough pkts to be sent */
> > -	if (unlikely(len == MAX_PKT_BURST)) {
> > -		send_burst(qconf, MAX_PKT_BURST, port);
> > +	if (unlikely(len == tx_pkt_burst)) {
> > +		send_burst(qconf, tx_pkt_burst, port);
> >   		len = 0;
> >   	}
> >
> > diff --git a/examples/l3fwd/l3fwd_acl.c b/examples/l3fwd/l3fwd_acl.c
> > index 4fc4b986cce6..a5af82357a03 100644
> > --- a/examples/l3fwd/l3fwd_acl.c
> > +++ b/examples/l3fwd/l3fwd_acl.c
> > @@ -1136,7 +1136,7 @@ acl_main_loop(__rte_unused void *dummy)
> >   			portid = qconf->rx_queue_list[i].port_id;
> >   			queueid = qconf->rx_queue_list[i].queue_id;
> >   			nb_rx = rte_eth_rx_burst(portid, queueid,
> > -				pkts_burst, nb_pkt_per_burst);
> > +				pkts_burst, rx_pkt_burst);
> >
> >   			if (nb_rx > 0) {
> >   				nb_drop = acl_process_pkts(pkts_burst, hops,
> > diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
> > index d94e5f135791..34fe70b9415c 100644
> > --- a/examples/l3fwd/l3fwd_common.h
> > +++ b/examples/l3fwd/l3fwd_common.h
> > @@ -71,7 +71,7 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
> >   	 * If TX buffer for that queue is empty, and we have enough packets,
> >   	 * then send them straightway.
> >   	 */
> > -	if (num >= MAX_TX_BURST && len == 0) {
> > +	if (num >= tx_pkt_burst / 2 && len == 0) {
> >   		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
> >   		if (unlikely(n < num)) {
> >   			do {
> > diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
> > index da9c45e3a482..ea74506ed971 100644
> > --- a/examples/l3fwd/l3fwd_em.c
> > +++ b/examples/l3fwd/l3fwd_em.c
> > @@ -644,7 +644,7 @@ em_main_loop(__rte_unused void *dummy)
> >   			portid = qconf->rx_queue_list[i].port_id;
> >   			queueid = qconf->rx_queue_list[i].queue_id;
> >   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> > -				nb_pkt_per_burst);
> > +				rx_pkt_burst);
> >   			if (nb_rx == 0)
> >   				continue;
> >
> > diff --git a/examples/l3fwd/l3fwd_fib.c b/examples/l3fwd/l3fwd_fib.c
> > index 82f1739df778..4223540b30ae 100644
> > --- a/examples/l3fwd/l3fwd_fib.c
> > +++ b/examples/l3fwd/l3fwd_fib.c
> > @@ -239,7 +239,7 @@ fib_main_loop(__rte_unused void *dummy)
> >   			portid = qconf->rx_queue_list[i].port_id;
> >   			queueid = qconf->rx_queue_list[i].queue_id;
> >   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> > -					nb_pkt_per_burst);
> > +					rx_pkt_burst);
> >   			if (nb_rx == 0)
> >   				continue;
> >
> > diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
> > index fec0aeb79c6a..bd1307c43e70 100644
> > --- a/examples/l3fwd/l3fwd_lpm.c
> > +++ b/examples/l3fwd/l3fwd_lpm.c
> > @@ -205,7 +205,7 @@ lpm_main_loop(__rte_unused void *dummy)
> >   			portid = qconf->rx_queue_list[i].port_id;
> >   			queueid = qconf->rx_queue_list[i].queue_id;
> >   			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> > -				nb_pkt_per_burst);
> > +				rx_pkt_burst);
> >   			if (nb_rx == 0)
> >   				continue;
> >
> > diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
> > index 994b7dd8e596..48453faf7c56 100644
> > --- a/examples/l3fwd/main.c
> > +++ b/examples/l3fwd/main.c
> > @@ -57,7 +57,8 @@
> >   static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST, "MAX_PKT_BURST should be at most MEMPOOL_CACHE_SIZE");
> >   uint16_t nb_rxd = RX_DESC_DEFAULT;
> >   uint16_t nb_txd = TX_DESC_DEFAULT;
> > -uint32_t nb_pkt_per_burst = DEFAULT_PKT_BURST;
> > +uint32_t rx_pkt_burst = DEFAULT_PKT_BURST;
> > +uint32_t tx_pkt_burst = DEFAULT_PKT_BURST;
> >   uint32_t mb_mempool_cache_size = MEMPOOL_CACHE_SIZE;
> >
> >   /**< Ports set in promiscuous mode off by default. */
> > @@ -399,7 +400,8 @@ print_usage(const char *prgname)
> >   		" --config (port,queue,lcore)[,(port,queue,lcore)]"
> >   		" [--rx-queue-size NPKTS]"
> >   		" [--tx-queue-size NPKTS]"
> > -		" [--burst NPKTS]"
> > +		" [--rx-burst NPKTS]"
> > +		" [--tx-burst NPKTS]"
> >   		" [--mbcache CACHESZ]"
> >   		" [--eth-dest=X,MM:MM:MM:MM:MM:MM]"
> >   		" [--max-pkt-len PKTLEN]"
> > @@ -426,8 +428,10 @@ print_usage(const char *prgname)
> >   		"            Default: %d\n"
> >   		"  --tx-queue-size NPKTS: Tx queue size in decimal\n"
> >   		"            Default: %d\n"
> > -		"  --burst NPKTS: Burst size in decimal\n"
> > -		"            Default: %d\n"
> > +		"  --rx-burst NPKTS: RX Burst size in decimal\n"
> > +		"            Default: %d, Maximum: %d\n"
> > +		"  --tx-burst NPKTS: TX Burst size in decimal\n"
> > +		"            Default: %d, Maximum: %d\n"
> >   		"  --mbcache CACHESZ: Mbuf cache size in decimal\n"
> >   		"            Default: %d\n"
> >   		"  --eth-dest=X,MM:MM:MM:MM:MM:MM: Ethernet destination for port X\n"
> > @@ -459,7 +463,10 @@ print_usage(const char *prgname)
> >   		"                    another is route entry at while line leads with character '%c'.\n"
> >   		"  --rule_ipv6=FILE: Specify the ipv6 rules entries file.\n"
> >   		"  --alg: ACL classify method to use, one of: %s.\n\n",
> > -		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT, DEFAULT_PKT_BURST, MEMPOOL_CACHE_SIZE,
> > +		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT,
> > +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> > +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> > +		MEMPOOL_CACHE_SIZE,
> >   		ACL_LEAD_CHAR, ROUTE_LEAD_CHAR, alg);
> >   }
> >
> > @@ -693,47 +700,30 @@ parse_mbcache_size(const char *optarg)
> >   			 RTE_MEMPOOL_CACHE_MAX_SIZE);
> >   }
> >
> > -static void
> > -parse_pkt_burst(const char *optarg)
> > +static int
> > +parse_pkt_burst(const char *optarg, bool is_rx)
> >   {
> > -	struct rte_eth_dev_info dev_info;
> >   	unsigned long pkt_burst;
> > -	uint16_t burst_size;
> >   	char *end = NULL;
> > -	int ret;
> >
> >   	/* parse decimal string */
> >   	pkt_burst = strtoul(optarg, &end, 10);
> > -	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0'))
> > -		return;
> > -
> > -	if (pkt_burst > MAX_PKT_BURST) {
> > -		RTE_LOG(INFO, L3FWD, "User provided burst must be <= %d. Using default value %d\n",
> > -			MAX_PKT_BURST, nb_pkt_per_burst);
> > -		return;
> > -	} else if (pkt_burst > 0) {
> > -		nb_pkt_per_burst = (uint32_t)pkt_burst;
> > -		return;
> > +	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0')) {
> > +		RTE_LOG(ERR, L3FWD, "Invalid %s-burst\n", is_rx ? "rx" : "tx");
> > +		return -1;
> >   	}
> >
> > -	/* If user gives a value of zero, query the PMD for its recommended Rx burst size. */
> > -	ret = rte_eth_dev_info_get(0, &dev_info);
> > -	if (ret != 0)
> > -		return;
> > -	burst_size = dev_info.default_rxportconf.burst_size;
> > -	if (burst_size == 0) {
> > -		RTE_LOG(INFO, L3FWD, "PMD does not recommend a burst size. Using default value %d. "
> > -			"User provided value must be in [1, %d]\n",
> > -			nb_pkt_per_burst, MAX_PKT_BURST);
> > -		return;
> > -	} else if (burst_size > MAX_PKT_BURST) {
> > -		RTE_LOG(INFO, L3FWD, "PMD recommended burst size %d exceeds maximum value %d. "
> > -			"Using default value %d\n",
> > -			burst_size, MAX_PKT_BURST, nb_pkt_per_burst);
> > -		return;
> > +	if (pkt_burst > MAX_PKT_BURST || pkt_burst == 0) {
> > +		RTE_LOG(ERR, L3FWD, "User-provided %s burst must be in (0, %d].\n",
> > +			is_rx ? "Rx" : "Tx", MAX_PKT_BURST);
> > +		return -1;
> > +	} else if (pkt_burst > 0) {
> > +		if (is_rx)
> > +			rx_pkt_burst = (uint16_t)pkt_burst;
> > +		else
> > +			tx_pkt_burst = (uint16_t)pkt_burst;
> >   	}
> > -	nb_pkt_per_burst = burst_size;
> > -	RTE_LOG(INFO, L3FWD, "Using PMD-provided burst value %d\n", burst_size);
> > +	return 0;
> >   }
> >
> >   #define MAX_JUMBO_PKT_LEN  9600
> > @@ -767,7 +757,8 @@ static const char short_options[] =
> >   #define CMD_LINE_OPT_RULE_IPV4 "rule_ipv4"
> >   #define CMD_LINE_OPT_RULE_IPV6 "rule_ipv6"
> >   #define CMD_LINE_OPT_ALG "alg"
> > -#define CMD_LINE_OPT_PKT_BURST "burst"
> > +#define CMD_LINE_OPT_PKT_RX_BURST "rx-burst"
> > +#define CMD_LINE_OPT_PKT_TX_BURST "tx-burst"
> >   #define CMD_LINE_OPT_MB_CACHE_SIZE "mbcache"
> >
> >   enum {
> > @@ -798,7 +789,8 @@ enum {
> >   	CMD_LINE_OPT_ENABLE_VECTOR_NUM,
> >   	CMD_LINE_OPT_VECTOR_SIZE_NUM,
> >   	CMD_LINE_OPT_VECTOR_TMO_NS_NUM,
> > -	CMD_LINE_OPT_PKT_BURST_NUM,
> > +	CMD_LINE_OPT_RX_PKT_BURST_NUM,
> > +	CMD_LINE_OPT_TX_PKT_BURST_NUM,
> >   	CMD_LINE_OPT_MB_CACHE_SIZE_NUM,
> >   };
> >
> > @@ -826,7 +818,8 @@ static const struct option lgopts[] = {
> >   	{CMD_LINE_OPT_RULE_IPV4,   1, 0, CMD_LINE_OPT_RULE_IPV4_NUM},
> >   	{CMD_LINE_OPT_RULE_IPV6,   1, 0, CMD_LINE_OPT_RULE_IPV6_NUM},
> >   	{CMD_LINE_OPT_ALG,   1, 0, CMD_LINE_OPT_ALG_NUM},
> > -	{CMD_LINE_OPT_PKT_BURST,   1, 0, CMD_LINE_OPT_PKT_BURST_NUM},
> > +	{CMD_LINE_OPT_PKT_RX_BURST,   1, 0, CMD_LINE_OPT_RX_PKT_BURST_NUM},
> > +	{CMD_LINE_OPT_PKT_TX_BURST,   1, 0, CMD_LINE_OPT_TX_PKT_BURST_NUM},
> >   	{CMD_LINE_OPT_MB_CACHE_SIZE,   1, 0, CMD_LINE_OPT_MB_CACHE_SIZE_NUM},
> >   	{NULL, 0, 0, 0}
> >   };
> > @@ -916,8 +909,20 @@ parse_args(int argc, char **argv)
> >   			parse_queue_size(optarg, &nb_txd, 0);
> >   			break;
> >
> > -		case CMD_LINE_OPT_PKT_BURST_NUM:
> > -			parse_pkt_burst(optarg);
> > +		case CMD_LINE_OPT_TX_PKT_BURST_NUM:
> > +			ret = parse_pkt_burst(optarg, false);
> > +			if (ret) {
> > +				print_usage(prgname);
> > +				return -1;
> > +			}
> > +			break;
> > +
> > +		case CMD_LINE_OPT_RX_PKT_BURST_NUM:
> > +			ret = parse_pkt_burst(optarg, true);
> > +			if (ret) {
> > +				print_usage(prgname);
> > +				return -1;
> > +			}
> >   			break;
> >
> >   		case CMD_LINE_OPT_MB_CACHE_SIZE_NUM:
  
Jie Hai Feb. 21, 2025, 3:42 a.m. UTC | #4
On 2025/2/20 1:01, Konstantin Ananyev wrote:
> 
> 
> 
>> On 2024/12/4 10:06, Jie Hai wrote:
>>> The application send packets only when the buffer is full, or the
>>> buffer is empty and the packets to be sent extends TX_PKT_BURST.
>>> The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
>>> increase, while the default cache size is 256. The packets in
>>> the TX direction occupy the cache. As a result, the performance
>>> deteriorates.
>>>
>>> Restore the default Tx burst and add option '--tx-burst' to set
>>> the Tx burst size. To ensure consistency, rename the option
>>> '--burst' to '--rx-burst'. The valid range of the user-provided
>>> value is (0, MAX_PKT_BURST] for both directions.
>>>
>>> Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
>>> Cc: stable@dpdk.org
> 
> Wouldn't that patch:
> https://patchwork.dpdk.org/project/dpdk/patch/20250212045416.2393001-1-sivaprasad.tummala@amd.com/
> fix that issue too?
> And probably in a less disruptive manner?
> 
Thanks for your comment.

I think different drivers may need different values for better 
performance, it makes sense to add options.

>>> Signed-off-by: Jie Hai <haijie1@huawei.com>
>>> ---
>>>    examples/l3fwd/l3fwd.h        | 14 +++---
>>>    examples/l3fwd/l3fwd_acl.c    |  2 +-
>>>    examples/l3fwd/l3fwd_common.h |  2 +-
>>>    examples/l3fwd/l3fwd_em.c     |  2 +-
>>>    examples/l3fwd/l3fwd_fib.c    |  2 +-
>>>    examples/l3fwd/l3fwd_lpm.c    |  2 +-
>>>    examples/l3fwd/main.c         | 89 ++++++++++++++++++-----------------
>>>    7 files changed, 59 insertions(+), 54 deletions(-)
>>>
>>> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
>>> index 0cce3406ee7d..a4e23b817edf 100644
>>> --- a/examples/l3fwd/l3fwd.h
>>> +++ b/examples/l3fwd/l3fwd.h
>>> @@ -32,10 +32,6 @@
>>>
>>>    #define VECTOR_SIZE_DEFAULT   MAX_PKT_BURST
>>>    #define VECTOR_TMO_NS_DEFAULT 1E6 /* 1ms */
>>> -/*
>>> - * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
>>> - */
>>> -#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
>>>
>>>    #define NB_SOCKETS        8
>>>
>>> @@ -116,7 +112,11 @@ extern struct acl_algorithms acl_alg[];
>>>
>>>    extern uint32_t max_pkt_len;
>>>
>>> -extern uint32_t nb_pkt_per_burst;
>>> +extern uint32_t rx_pkt_burst;
>>> +/*
>>> + * Try to avoid TX buffering if we have at least tx_pkt_burst packets to send.
>>> + */
>>> +extern uint32_t tx_pkt_burst;
>>>    extern uint32_t mb_mempool_cache_size;
>>>
>>>    /* Send burst of packets on an output interface */
>>> @@ -152,8 +152,8 @@ send_single_packet(struct lcore_conf *qconf,
>>>    	len++;
>>>
>>>    	/* enough pkts to be sent */
>>> -	if (unlikely(len == MAX_PKT_BURST)) {
>>> -		send_burst(qconf, MAX_PKT_BURST, port);
>>> +	if (unlikely(len == tx_pkt_burst)) {
>>> +		send_burst(qconf, tx_pkt_burst, port);
>>>    		len = 0;
>>>    	}
>>>
>>> diff --git a/examples/l3fwd/l3fwd_acl.c b/examples/l3fwd/l3fwd_acl.c
>>> index 4fc4b986cce6..a5af82357a03 100644
>>> --- a/examples/l3fwd/l3fwd_acl.c
>>> +++ b/examples/l3fwd/l3fwd_acl.c
>>> @@ -1136,7 +1136,7 @@ acl_main_loop(__rte_unused void *dummy)
>>>    			portid = qconf->rx_queue_list[i].port_id;
>>>    			queueid = qconf->rx_queue_list[i].queue_id;
>>>    			nb_rx = rte_eth_rx_burst(portid, queueid,
>>> -				pkts_burst, nb_pkt_per_burst);
>>> +				pkts_burst, rx_pkt_burst);
>>>
>>>    			if (nb_rx > 0) {
>>>    				nb_drop = acl_process_pkts(pkts_burst, hops,
>>> diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
>>> index d94e5f135791..34fe70b9415c 100644
>>> --- a/examples/l3fwd/l3fwd_common.h
>>> +++ b/examples/l3fwd/l3fwd_common.h
>>> @@ -71,7 +71,7 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
>>>    	 * If TX buffer for that queue is empty, and we have enough packets,
>>>    	 * then send them straightway.
>>>    	 */
>>> -	if (num >= MAX_TX_BURST && len == 0) {
>>> +	if (num >= tx_pkt_burst / 2 && len == 0) {
>>>    		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
>>>    		if (unlikely(n < num)) {
>>>    			do {
>>> diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
>>> index da9c45e3a482..ea74506ed971 100644
>>> --- a/examples/l3fwd/l3fwd_em.c
>>> +++ b/examples/l3fwd/l3fwd_em.c
>>> @@ -644,7 +644,7 @@ em_main_loop(__rte_unused void *dummy)
>>>    			portid = qconf->rx_queue_list[i].port_id;
>>>    			queueid = qconf->rx_queue_list[i].queue_id;
>>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
>>> -				nb_pkt_per_burst);
>>> +				rx_pkt_burst);
>>>    			if (nb_rx == 0)
>>>    				continue;
>>>
>>> diff --git a/examples/l3fwd/l3fwd_fib.c b/examples/l3fwd/l3fwd_fib.c
>>> index 82f1739df778..4223540b30ae 100644
>>> --- a/examples/l3fwd/l3fwd_fib.c
>>> +++ b/examples/l3fwd/l3fwd_fib.c
>>> @@ -239,7 +239,7 @@ fib_main_loop(__rte_unused void *dummy)
>>>    			portid = qconf->rx_queue_list[i].port_id;
>>>    			queueid = qconf->rx_queue_list[i].queue_id;
>>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
>>> -					nb_pkt_per_burst);
>>> +					rx_pkt_burst);
>>>    			if (nb_rx == 0)
>>>    				continue;
>>>
>>> diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
>>> index fec0aeb79c6a..bd1307c43e70 100644
>>> --- a/examples/l3fwd/l3fwd_lpm.c
>>> +++ b/examples/l3fwd/l3fwd_lpm.c
>>> @@ -205,7 +205,7 @@ lpm_main_loop(__rte_unused void *dummy)
>>>    			portid = qconf->rx_queue_list[i].port_id;
>>>    			queueid = qconf->rx_queue_list[i].queue_id;
>>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
>>> -				nb_pkt_per_burst);
>>> +				rx_pkt_burst);
>>>    			if (nb_rx == 0)
>>>    				continue;
>>>
>>> diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
>>> index 994b7dd8e596..48453faf7c56 100644
>>> --- a/examples/l3fwd/main.c
>>> +++ b/examples/l3fwd/main.c
>>> @@ -57,7 +57,8 @@
>>>    static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST, "MAX_PKT_BURST should be at most MEMPOOL_CACHE_SIZE");
>>>    uint16_t nb_rxd = RX_DESC_DEFAULT;
>>>    uint16_t nb_txd = TX_DESC_DEFAULT;
>>> -uint32_t nb_pkt_per_burst = DEFAULT_PKT_BURST;
>>> +uint32_t rx_pkt_burst = DEFAULT_PKT_BURST;
>>> +uint32_t tx_pkt_burst = DEFAULT_PKT_BURST;
>>>    uint32_t mb_mempool_cache_size = MEMPOOL_CACHE_SIZE;
>>>
>>>    /**< Ports set in promiscuous mode off by default. */
>>> @@ -399,7 +400,8 @@ print_usage(const char *prgname)
>>>    		" --config (port,queue,lcore)[,(port,queue,lcore)]"
>>>    		" [--rx-queue-size NPKTS]"
>>>    		" [--tx-queue-size NPKTS]"
>>> -		" [--burst NPKTS]"
>>> +		" [--rx-burst NPKTS]"
>>> +		" [--tx-burst NPKTS]"
>>>    		" [--mbcache CACHESZ]"
>>>    		" [--eth-dest=X,MM:MM:MM:MM:MM:MM]"
>>>    		" [--max-pkt-len PKTLEN]"
>>> @@ -426,8 +428,10 @@ print_usage(const char *prgname)
>>>    		"            Default: %d\n"
>>>    		"  --tx-queue-size NPKTS: Tx queue size in decimal\n"
>>>    		"            Default: %d\n"
>>> -		"  --burst NPKTS: Burst size in decimal\n"
>>> -		"            Default: %d\n"
>>> +		"  --rx-burst NPKTS: RX Burst size in decimal\n"
>>> +		"            Default: %d, Maximum: %d\n"
>>> +		"  --tx-burst NPKTS: TX Burst size in decimal\n"
>>> +		"            Default: %d, Maximum: %d\n"
>>>    		"  --mbcache CACHESZ: Mbuf cache size in decimal\n"
>>>    		"            Default: %d\n"
>>>    		"  --eth-dest=X,MM:MM:MM:MM:MM:MM: Ethernet destination for port X\n"
>>> @@ -459,7 +463,10 @@ print_usage(const char *prgname)
>>>    		"                    another is route entry at while line leads with character '%c'.\n"
>>>    		"  --rule_ipv6=FILE: Specify the ipv6 rules entries file.\n"
>>>    		"  --alg: ACL classify method to use, one of: %s.\n\n",
>>> -		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT, DEFAULT_PKT_BURST, MEMPOOL_CACHE_SIZE,
>>> +		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT,
>>> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
>>> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
>>> +		MEMPOOL_CACHE_SIZE,
>>>    		ACL_LEAD_CHAR, ROUTE_LEAD_CHAR, alg);
>>>    }
>>>
>>> @@ -693,47 +700,30 @@ parse_mbcache_size(const char *optarg)
>>>    			 RTE_MEMPOOL_CACHE_MAX_SIZE);
>>>    }
>>>
>>> -static void
>>> -parse_pkt_burst(const char *optarg)
>>> +static int
>>> +parse_pkt_burst(const char *optarg, bool is_rx)
>>>    {
>>> -	struct rte_eth_dev_info dev_info;
>>>    	unsigned long pkt_burst;
>>> -	uint16_t burst_size;
>>>    	char *end = NULL;
>>> -	int ret;
>>>
>>>    	/* parse decimal string */
>>>    	pkt_burst = strtoul(optarg, &end, 10);
>>> -	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0'))
>>> -		return;
>>> -
>>> -	if (pkt_burst > MAX_PKT_BURST) {
>>> -		RTE_LOG(INFO, L3FWD, "User provided burst must be <= %d. Using default value %d\n",
>>> -			MAX_PKT_BURST, nb_pkt_per_burst);
>>> -		return;
>>> -	} else if (pkt_burst > 0) {
>>> -		nb_pkt_per_burst = (uint32_t)pkt_burst;
>>> -		return;
>>> +	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0')) {
>>> +		RTE_LOG(ERR, L3FWD, "Invalid %s-burst\n", is_rx ? "rx" : "tx");
>>> +		return -1;
>>>    	}
>>>
>>> -	/* If user gives a value of zero, query the PMD for its recommended Rx burst size. */
>>> -	ret = rte_eth_dev_info_get(0, &dev_info);
>>> -	if (ret != 0)
>>> -		return;
>>> -	burst_size = dev_info.default_rxportconf.burst_size;
>>> -	if (burst_size == 0) {
>>> -		RTE_LOG(INFO, L3FWD, "PMD does not recommend a burst size. Using default value %d. "
>>> -			"User provided value must be in [1, %d]\n",
>>> -			nb_pkt_per_burst, MAX_PKT_BURST);
>>> -		return;
>>> -	} else if (burst_size > MAX_PKT_BURST) {
>>> -		RTE_LOG(INFO, L3FWD, "PMD recommended burst size %d exceeds maximum value %d. "
>>> -			"Using default value %d\n",
>>> -			burst_size, MAX_PKT_BURST, nb_pkt_per_burst);
>>> -		return;
>>> +	if (pkt_burst > MAX_PKT_BURST || pkt_burst == 0) {
>>> +		RTE_LOG(ERR, L3FWD, "User-provided %s burst must be in (0, %d].\n",
>>> +			is_rx ? "Rx" : "Tx", MAX_PKT_BURST);
>>> +		return -1;
>>> +	} else if (pkt_burst > 0) {
>>> +		if (is_rx)
>>> +			rx_pkt_burst = (uint16_t)pkt_burst;
>>> +		else
>>> +			tx_pkt_burst = (uint16_t)pkt_burst;
>>>    	}
>>> -	nb_pkt_per_burst = burst_size;
>>> -	RTE_LOG(INFO, L3FWD, "Using PMD-provided burst value %d\n", burst_size);
>>> +	return 0;
>>>    }
>>>
>>>    #define MAX_JUMBO_PKT_LEN  9600
>>> @@ -767,7 +757,8 @@ static const char short_options[] =
>>>    #define CMD_LINE_OPT_RULE_IPV4 "rule_ipv4"
>>>    #define CMD_LINE_OPT_RULE_IPV6 "rule_ipv6"
>>>    #define CMD_LINE_OPT_ALG "alg"
>>> -#define CMD_LINE_OPT_PKT_BURST "burst"
>>> +#define CMD_LINE_OPT_PKT_RX_BURST "rx-burst"
>>> +#define CMD_LINE_OPT_PKT_TX_BURST "tx-burst"
>>>    #define CMD_LINE_OPT_MB_CACHE_SIZE "mbcache"
>>>
>>>    enum {
>>> @@ -798,7 +789,8 @@ enum {
>>>    	CMD_LINE_OPT_ENABLE_VECTOR_NUM,
>>>    	CMD_LINE_OPT_VECTOR_SIZE_NUM,
>>>    	CMD_LINE_OPT_VECTOR_TMO_NS_NUM,
>>> -	CMD_LINE_OPT_PKT_BURST_NUM,
>>> +	CMD_LINE_OPT_RX_PKT_BURST_NUM,
>>> +	CMD_LINE_OPT_TX_PKT_BURST_NUM,
>>>    	CMD_LINE_OPT_MB_CACHE_SIZE_NUM,
>>>    };
>>>
>>> @@ -826,7 +818,8 @@ static const struct option lgopts[] = {
>>>    	{CMD_LINE_OPT_RULE_IPV4,   1, 0, CMD_LINE_OPT_RULE_IPV4_NUM},
>>>    	{CMD_LINE_OPT_RULE_IPV6,   1, 0, CMD_LINE_OPT_RULE_IPV6_NUM},
>>>    	{CMD_LINE_OPT_ALG,   1, 0, CMD_LINE_OPT_ALG_NUM},
>>> -	{CMD_LINE_OPT_PKT_BURST,   1, 0, CMD_LINE_OPT_PKT_BURST_NUM},
>>> +	{CMD_LINE_OPT_PKT_RX_BURST,   1, 0, CMD_LINE_OPT_RX_PKT_BURST_NUM},
>>> +	{CMD_LINE_OPT_PKT_TX_BURST,   1, 0, CMD_LINE_OPT_TX_PKT_BURST_NUM},
>>>    	{CMD_LINE_OPT_MB_CACHE_SIZE,   1, 0, CMD_LINE_OPT_MB_CACHE_SIZE_NUM},
>>>    	{NULL, 0, 0, 0}
>>>    };
>>> @@ -916,8 +909,20 @@ parse_args(int argc, char **argv)
>>>    			parse_queue_size(optarg, &nb_txd, 0);
>>>    			break;
>>>
>>> -		case CMD_LINE_OPT_PKT_BURST_NUM:
>>> -			parse_pkt_burst(optarg);
>>> +		case CMD_LINE_OPT_TX_PKT_BURST_NUM:
>>> +			ret = parse_pkt_burst(optarg, false);
>>> +			if (ret) {
>>> +				print_usage(prgname);
>>> +				return -1;
>>> +			}
>>> +			break;
>>> +
>>> +		case CMD_LINE_OPT_RX_PKT_BURST_NUM:
>>> +			ret = parse_pkt_burst(optarg, true);
>>> +			if (ret) {
>>> +				print_usage(prgname);
>>> +				return -1;
>>> +			}
>>>    			break;
>>>
>>>    		case CMD_LINE_OPT_MB_CACHE_SIZE_NUM:
  
Konstantin Ananyev Feb. 21, 2025, 8:45 a.m. UTC | #5
> >> On 2024/12/4 10:06, Jie Hai wrote:
> >>> The application send packets only when the buffer is full, or the
> >>> buffer is empty and the packets to be sent extends TX_PKT_BURST.
> >>> The change of MAX_PKT_BURST make TX buffer size and TX_PKT_BURST
> >>> increase, while the default cache size is 256. The packets in
> >>> the TX direction occupy the cache. As a result, the performance
> >>> deteriorates.
> >>>
> >>> Restore the default Tx burst and add option '--tx-burst' to set
> >>> the Tx burst size. To ensure consistency, rename the option
> >>> '--burst' to '--rx-burst'. The valid range of the user-provided
> >>> value is (0, MAX_PKT_BURST] for both directions.
> >>>
> >>> Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set RX burst size")
> >>> Cc: stable@dpdk.org
> >
> > Wouldn't that patch:
> > https://patchwork.dpdk.org/project/dpdk/patch/20250212045416.2393001-1-sivaprasad.tummala@amd.com/
> > fix that issue too?
> > And probably in a less disruptive manner?
> >
> Thanks for your comment.
> 
> I think different drivers may need different values for better
> performance, it makes sense to add options.

 Well, we used to run l3fwd for more then 10 years by now,
and I don’t' remember that anyone claim that it is needed.
Again, AFAIR, our other sample apps including test-pmd uses
one burst size for both RX and TX.
Do you have any perf numbers to back-up your claim?  
 
> 
> >>> Signed-off-by: Jie Hai <haijie1@huawei.com>
> >>> ---
> >>>    examples/l3fwd/l3fwd.h        | 14 +++---
> >>>    examples/l3fwd/l3fwd_acl.c    |  2 +-
> >>>    examples/l3fwd/l3fwd_common.h |  2 +-
> >>>    examples/l3fwd/l3fwd_em.c     |  2 +-
> >>>    examples/l3fwd/l3fwd_fib.c    |  2 +-
> >>>    examples/l3fwd/l3fwd_lpm.c    |  2 +-
> >>>    examples/l3fwd/main.c         | 89 ++++++++++++++++++-----------------
> >>>    7 files changed, 59 insertions(+), 54 deletions(-)
> >>>
> >>> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
> >>> index 0cce3406ee7d..a4e23b817edf 100644
> >>> --- a/examples/l3fwd/l3fwd.h
> >>> +++ b/examples/l3fwd/l3fwd.h
> >>> @@ -32,10 +32,6 @@
> >>>
> >>>    #define VECTOR_SIZE_DEFAULT   MAX_PKT_BURST
> >>>    #define VECTOR_TMO_NS_DEFAULT 1E6 /* 1ms */
> >>> -/*
> >>> - * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
> >>> - */
> >>> -#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
> >>>
> >>>    #define NB_SOCKETS        8
> >>>
> >>> @@ -116,7 +112,11 @@ extern struct acl_algorithms acl_alg[];
> >>>
> >>>    extern uint32_t max_pkt_len;
> >>>
> >>> -extern uint32_t nb_pkt_per_burst;
> >>> +extern uint32_t rx_pkt_burst;
> >>> +/*
> >>> + * Try to avoid TX buffering if we have at least tx_pkt_burst packets to send.
> >>> + */
> >>> +extern uint32_t tx_pkt_burst;
> >>>    extern uint32_t mb_mempool_cache_size;
> >>>
> >>>    /* Send burst of packets on an output interface */
> >>> @@ -152,8 +152,8 @@ send_single_packet(struct lcore_conf *qconf,
> >>>    	len++;
> >>>
> >>>    	/* enough pkts to be sent */
> >>> -	if (unlikely(len == MAX_PKT_BURST)) {
> >>> -		send_burst(qconf, MAX_PKT_BURST, port);
> >>> +	if (unlikely(len == tx_pkt_burst)) {
> >>> +		send_burst(qconf, tx_pkt_burst, port);
> >>>    		len = 0;
> >>>    	}
> >>>
> >>> diff --git a/examples/l3fwd/l3fwd_acl.c b/examples/l3fwd/l3fwd_acl.c
> >>> index 4fc4b986cce6..a5af82357a03 100644
> >>> --- a/examples/l3fwd/l3fwd_acl.c
> >>> +++ b/examples/l3fwd/l3fwd_acl.c
> >>> @@ -1136,7 +1136,7 @@ acl_main_loop(__rte_unused void *dummy)
> >>>    			portid = qconf->rx_queue_list[i].port_id;
> >>>    			queueid = qconf->rx_queue_list[i].queue_id;
> >>>    			nb_rx = rte_eth_rx_burst(portid, queueid,
> >>> -				pkts_burst, nb_pkt_per_burst);
> >>> +				pkts_burst, rx_pkt_burst);
> >>>
> >>>    			if (nb_rx > 0) {
> >>>    				nb_drop = acl_process_pkts(pkts_burst, hops,
> >>> diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
> >>> index d94e5f135791..34fe70b9415c 100644
> >>> --- a/examples/l3fwd/l3fwd_common.h
> >>> +++ b/examples/l3fwd/l3fwd_common.h
> >>> @@ -71,7 +71,7 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
> >>>    	 * If TX buffer for that queue is empty, and we have enough packets,
> >>>    	 * then send them straightway.
> >>>    	 */
> >>> -	if (num >= MAX_TX_BURST && len == 0) {
> >>> +	if (num >= tx_pkt_burst / 2 && len == 0) {
> >>>    		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
> >>>    		if (unlikely(n < num)) {
> >>>    			do {
> >>> diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
> >>> index da9c45e3a482..ea74506ed971 100644
> >>> --- a/examples/l3fwd/l3fwd_em.c
> >>> +++ b/examples/l3fwd/l3fwd_em.c
> >>> @@ -644,7 +644,7 @@ em_main_loop(__rte_unused void *dummy)
> >>>    			portid = qconf->rx_queue_list[i].port_id;
> >>>    			queueid = qconf->rx_queue_list[i].queue_id;
> >>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> >>> -				nb_pkt_per_burst);
> >>> +				rx_pkt_burst);
> >>>    			if (nb_rx == 0)
> >>>    				continue;
> >>>
> >>> diff --git a/examples/l3fwd/l3fwd_fib.c b/examples/l3fwd/l3fwd_fib.c
> >>> index 82f1739df778..4223540b30ae 100644
> >>> --- a/examples/l3fwd/l3fwd_fib.c
> >>> +++ b/examples/l3fwd/l3fwd_fib.c
> >>> @@ -239,7 +239,7 @@ fib_main_loop(__rte_unused void *dummy)
> >>>    			portid = qconf->rx_queue_list[i].port_id;
> >>>    			queueid = qconf->rx_queue_list[i].queue_id;
> >>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> >>> -					nb_pkt_per_burst);
> >>> +					rx_pkt_burst);
> >>>    			if (nb_rx == 0)
> >>>    				continue;
> >>>
> >>> diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
> >>> index fec0aeb79c6a..bd1307c43e70 100644
> >>> --- a/examples/l3fwd/l3fwd_lpm.c
> >>> +++ b/examples/l3fwd/l3fwd_lpm.c
> >>> @@ -205,7 +205,7 @@ lpm_main_loop(__rte_unused void *dummy)
> >>>    			portid = qconf->rx_queue_list[i].port_id;
> >>>    			queueid = qconf->rx_queue_list[i].queue_id;
> >>>    			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> >>> -				nb_pkt_per_burst);
> >>> +				rx_pkt_burst);
> >>>    			if (nb_rx == 0)
> >>>    				continue;
> >>>
> >>> diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
> >>> index 994b7dd8e596..48453faf7c56 100644
> >>> --- a/examples/l3fwd/main.c
> >>> +++ b/examples/l3fwd/main.c
> >>> @@ -57,7 +57,8 @@
> >>>    static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST, "MAX_PKT_BURST should be at most MEMPOOL_CACHE_SIZE");
> >>>    uint16_t nb_rxd = RX_DESC_DEFAULT;
> >>>    uint16_t nb_txd = TX_DESC_DEFAULT;
> >>> -uint32_t nb_pkt_per_burst = DEFAULT_PKT_BURST;
> >>> +uint32_t rx_pkt_burst = DEFAULT_PKT_BURST;
> >>> +uint32_t tx_pkt_burst = DEFAULT_PKT_BURST;
> >>>    uint32_t mb_mempool_cache_size = MEMPOOL_CACHE_SIZE;
> >>>
> >>>    /**< Ports set in promiscuous mode off by default. */
> >>> @@ -399,7 +400,8 @@ print_usage(const char *prgname)
> >>>    		" --config (port,queue,lcore)[,(port,queue,lcore)]"
> >>>    		" [--rx-queue-size NPKTS]"
> >>>    		" [--tx-queue-size NPKTS]"
> >>> -		" [--burst NPKTS]"
> >>> +		" [--rx-burst NPKTS]"
> >>> +		" [--tx-burst NPKTS]"
> >>>    		" [--mbcache CACHESZ]"
> >>>    		" [--eth-dest=X,MM:MM:MM:MM:MM:MM]"
> >>>    		" [--max-pkt-len PKTLEN]"
> >>> @@ -426,8 +428,10 @@ print_usage(const char *prgname)
> >>>    		"            Default: %d\n"
> >>>    		"  --tx-queue-size NPKTS: Tx queue size in decimal\n"
> >>>    		"            Default: %d\n"
> >>> -		"  --burst NPKTS: Burst size in decimal\n"
> >>> -		"            Default: %d\n"
> >>> +		"  --rx-burst NPKTS: RX Burst size in decimal\n"
> >>> +		"            Default: %d, Maximum: %d\n"
> >>> +		"  --tx-burst NPKTS: TX Burst size in decimal\n"
> >>> +		"            Default: %d, Maximum: %d\n"
> >>>    		"  --mbcache CACHESZ: Mbuf cache size in decimal\n"
> >>>    		"            Default: %d\n"
> >>>    		"  --eth-dest=X,MM:MM:MM:MM:MM:MM: Ethernet destination for port X\n"
> >>> @@ -459,7 +463,10 @@ print_usage(const char *prgname)
> >>>    		"                    another is route entry at while line leads with character '%c'.\n"
> >>>    		"  --rule_ipv6=FILE: Specify the ipv6 rules entries file.\n"
> >>>    		"  --alg: ACL classify method to use, one of: %s.\n\n",
> >>> -		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT, DEFAULT_PKT_BURST, MEMPOOL_CACHE_SIZE,
> >>> +		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT,
> >>> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> >>> +		DEFAULT_PKT_BURST, MAX_PKT_BURST,
> >>> +		MEMPOOL_CACHE_SIZE,
> >>>    		ACL_LEAD_CHAR, ROUTE_LEAD_CHAR, alg);
> >>>    }
> >>>
> >>> @@ -693,47 +700,30 @@ parse_mbcache_size(const char *optarg)
> >>>    			 RTE_MEMPOOL_CACHE_MAX_SIZE);
> >>>    }
> >>>
> >>> -static void
> >>> -parse_pkt_burst(const char *optarg)
> >>> +static int
> >>> +parse_pkt_burst(const char *optarg, bool is_rx)
> >>>    {
> >>> -	struct rte_eth_dev_info dev_info;
> >>>    	unsigned long pkt_burst;
> >>> -	uint16_t burst_size;
> >>>    	char *end = NULL;
> >>> -	int ret;
> >>>
> >>>    	/* parse decimal string */
> >>>    	pkt_burst = strtoul(optarg, &end, 10);
> >>> -	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0'))
> >>> -		return;
> >>> -
> >>> -	if (pkt_burst > MAX_PKT_BURST) {
> >>> -		RTE_LOG(INFO, L3FWD, "User provided burst must be <= %d. Using default value %d\n",
> >>> -			MAX_PKT_BURST, nb_pkt_per_burst);
> >>> -		return;
> >>> -	} else if (pkt_burst > 0) {
> >>> -		nb_pkt_per_burst = (uint32_t)pkt_burst;
> >>> -		return;
> >>> +	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0')) {
> >>> +		RTE_LOG(ERR, L3FWD, "Invalid %s-burst\n", is_rx ? "rx" : "tx");
> >>> +		return -1;
> >>>    	}
> >>>
> >>> -	/* If user gives a value of zero, query the PMD for its recommended Rx burst size. */
> >>> -	ret = rte_eth_dev_info_get(0, &dev_info);
> >>> -	if (ret != 0)
> >>> -		return;
> >>> -	burst_size = dev_info.default_rxportconf.burst_size;
> >>> -	if (burst_size == 0) {
> >>> -		RTE_LOG(INFO, L3FWD, "PMD does not recommend a burst size. Using default value %d. "
> >>> -			"User provided value must be in [1, %d]\n",
> >>> -			nb_pkt_per_burst, MAX_PKT_BURST);
> >>> -		return;
> >>> -	} else if (burst_size > MAX_PKT_BURST) {
> >>> -		RTE_LOG(INFO, L3FWD, "PMD recommended burst size %d exceeds maximum value %d. "
> >>> -			"Using default value %d\n",
> >>> -			burst_size, MAX_PKT_BURST, nb_pkt_per_burst);
> >>> -		return;
> >>> +	if (pkt_burst > MAX_PKT_BURST || pkt_burst == 0) {
> >>> +		RTE_LOG(ERR, L3FWD, "User-provided %s burst must be in (0, %d].\n",
> >>> +			is_rx ? "Rx" : "Tx", MAX_PKT_BURST);
> >>> +		return -1;
> >>> +	} else if (pkt_burst > 0) {
> >>> +		if (is_rx)
> >>> +			rx_pkt_burst = (uint16_t)pkt_burst;
> >>> +		else
> >>> +			tx_pkt_burst = (uint16_t)pkt_burst;
> >>>    	}
> >>> -	nb_pkt_per_burst = burst_size;
> >>> -	RTE_LOG(INFO, L3FWD, "Using PMD-provided burst value %d\n", burst_size);
> >>> +	return 0;
> >>>    }
> >>>
> >>>    #define MAX_JUMBO_PKT_LEN  9600
> >>> @@ -767,7 +757,8 @@ static const char short_options[] =
> >>>    #define CMD_LINE_OPT_RULE_IPV4 "rule_ipv4"
> >>>    #define CMD_LINE_OPT_RULE_IPV6 "rule_ipv6"
> >>>    #define CMD_LINE_OPT_ALG "alg"
> >>> -#define CMD_LINE_OPT_PKT_BURST "burst"
> >>> +#define CMD_LINE_OPT_PKT_RX_BURST "rx-burst"
> >>> +#define CMD_LINE_OPT_PKT_TX_BURST "tx-burst"
> >>>    #define CMD_LINE_OPT_MB_CACHE_SIZE "mbcache"
> >>>
> >>>    enum {
> >>> @@ -798,7 +789,8 @@ enum {
> >>>    	CMD_LINE_OPT_ENABLE_VECTOR_NUM,
> >>>    	CMD_LINE_OPT_VECTOR_SIZE_NUM,
> >>>    	CMD_LINE_OPT_VECTOR_TMO_NS_NUM,
> >>> -	CMD_LINE_OPT_PKT_BURST_NUM,
> >>> +	CMD_LINE_OPT_RX_PKT_BURST_NUM,
> >>> +	CMD_LINE_OPT_TX_PKT_BURST_NUM,
> >>>    	CMD_LINE_OPT_MB_CACHE_SIZE_NUM,
> >>>    };
> >>>
> >>> @@ -826,7 +818,8 @@ static const struct option lgopts[] = {
> >>>    	{CMD_LINE_OPT_RULE_IPV4,   1, 0, CMD_LINE_OPT_RULE_IPV4_NUM},
> >>>    	{CMD_LINE_OPT_RULE_IPV6,   1, 0, CMD_LINE_OPT_RULE_IPV6_NUM},
> >>>    	{CMD_LINE_OPT_ALG,   1, 0, CMD_LINE_OPT_ALG_NUM},
> >>> -	{CMD_LINE_OPT_PKT_BURST,   1, 0, CMD_LINE_OPT_PKT_BURST_NUM},
> >>> +	{CMD_LINE_OPT_PKT_RX_BURST,   1, 0, CMD_LINE_OPT_RX_PKT_BURST_NUM},
> >>> +	{CMD_LINE_OPT_PKT_TX_BURST,   1, 0, CMD_LINE_OPT_TX_PKT_BURST_NUM},
> >>>    	{CMD_LINE_OPT_MB_CACHE_SIZE,   1, 0, CMD_LINE_OPT_MB_CACHE_SIZE_NUM},
> >>>    	{NULL, 0, 0, 0}
> >>>    };
> >>> @@ -916,8 +909,20 @@ parse_args(int argc, char **argv)
> >>>    			parse_queue_size(optarg, &nb_txd, 0);
> >>>    			break;
> >>>
> >>> -		case CMD_LINE_OPT_PKT_BURST_NUM:
> >>> -			parse_pkt_burst(optarg);
> >>> +		case CMD_LINE_OPT_TX_PKT_BURST_NUM:
> >>> +			ret = parse_pkt_burst(optarg, false);
> >>> +			if (ret) {
> >>> +				print_usage(prgname);
> >>> +				return -1;
> >>> +			}
> >>> +			break;
> >>> +
> >>> +		case CMD_LINE_OPT_RX_PKT_BURST_NUM:
> >>> +			ret = parse_pkt_burst(optarg, true);
> >>> +			if (ret) {
> >>> +				print_usage(prgname);
> >>> +				return -1;
> >>> +			}
> >>>    			break;
> >>>
> >>>    		case CMD_LINE_OPT_MB_CACHE_SIZE_NUM:
  

Patch

diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
index 0cce3406ee7d..a4e23b817edf 100644
--- a/examples/l3fwd/l3fwd.h
+++ b/examples/l3fwd/l3fwd.h
@@ -32,10 +32,6 @@ 
 
 #define VECTOR_SIZE_DEFAULT   MAX_PKT_BURST
 #define VECTOR_TMO_NS_DEFAULT 1E6 /* 1ms */
-/*
- * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
- */
-#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
 
 #define NB_SOCKETS        8
 
@@ -116,7 +112,11 @@  extern struct acl_algorithms acl_alg[];
 
 extern uint32_t max_pkt_len;
 
-extern uint32_t nb_pkt_per_burst;
+extern uint32_t rx_pkt_burst;
+/*
+ * Try to avoid TX buffering if we have at least tx_pkt_burst packets to send.
+ */
+extern uint32_t tx_pkt_burst;
 extern uint32_t mb_mempool_cache_size;
 
 /* Send burst of packets on an output interface */
@@ -152,8 +152,8 @@  send_single_packet(struct lcore_conf *qconf,
 	len++;
 
 	/* enough pkts to be sent */
-	if (unlikely(len == MAX_PKT_BURST)) {
-		send_burst(qconf, MAX_PKT_BURST, port);
+	if (unlikely(len == tx_pkt_burst)) {
+		send_burst(qconf, tx_pkt_burst, port);
 		len = 0;
 	}
 
diff --git a/examples/l3fwd/l3fwd_acl.c b/examples/l3fwd/l3fwd_acl.c
index 4fc4b986cce6..a5af82357a03 100644
--- a/examples/l3fwd/l3fwd_acl.c
+++ b/examples/l3fwd/l3fwd_acl.c
@@ -1136,7 +1136,7 @@  acl_main_loop(__rte_unused void *dummy)
 			portid = qconf->rx_queue_list[i].port_id;
 			queueid = qconf->rx_queue_list[i].queue_id;
 			nb_rx = rte_eth_rx_burst(portid, queueid,
-				pkts_burst, nb_pkt_per_burst);
+				pkts_burst, rx_pkt_burst);
 
 			if (nb_rx > 0) {
 				nb_drop = acl_process_pkts(pkts_burst, hops,
diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
index d94e5f135791..34fe70b9415c 100644
--- a/examples/l3fwd/l3fwd_common.h
+++ b/examples/l3fwd/l3fwd_common.h
@@ -71,7 +71,7 @@  send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
 	 * If TX buffer for that queue is empty, and we have enough packets,
 	 * then send them straightway.
 	 */
-	if (num >= MAX_TX_BURST && len == 0) {
+	if (num >= tx_pkt_burst / 2 && len == 0) {
 		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
 		if (unlikely(n < num)) {
 			do {
diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
index da9c45e3a482..ea74506ed971 100644
--- a/examples/l3fwd/l3fwd_em.c
+++ b/examples/l3fwd/l3fwd_em.c
@@ -644,7 +644,7 @@  em_main_loop(__rte_unused void *dummy)
 			portid = qconf->rx_queue_list[i].port_id;
 			queueid = qconf->rx_queue_list[i].queue_id;
 			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
-				nb_pkt_per_burst);
+				rx_pkt_burst);
 			if (nb_rx == 0)
 				continue;
 
diff --git a/examples/l3fwd/l3fwd_fib.c b/examples/l3fwd/l3fwd_fib.c
index 82f1739df778..4223540b30ae 100644
--- a/examples/l3fwd/l3fwd_fib.c
+++ b/examples/l3fwd/l3fwd_fib.c
@@ -239,7 +239,7 @@  fib_main_loop(__rte_unused void *dummy)
 			portid = qconf->rx_queue_list[i].port_id;
 			queueid = qconf->rx_queue_list[i].queue_id;
 			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
-					nb_pkt_per_burst);
+					rx_pkt_burst);
 			if (nb_rx == 0)
 				continue;
 
diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
index fec0aeb79c6a..bd1307c43e70 100644
--- a/examples/l3fwd/l3fwd_lpm.c
+++ b/examples/l3fwd/l3fwd_lpm.c
@@ -205,7 +205,7 @@  lpm_main_loop(__rte_unused void *dummy)
 			portid = qconf->rx_queue_list[i].port_id;
 			queueid = qconf->rx_queue_list[i].queue_id;
 			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
-				nb_pkt_per_burst);
+				rx_pkt_burst);
 			if (nb_rx == 0)
 				continue;
 
diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
index 994b7dd8e596..48453faf7c56 100644
--- a/examples/l3fwd/main.c
+++ b/examples/l3fwd/main.c
@@ -57,7 +57,8 @@ 
 static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST, "MAX_PKT_BURST should be at most MEMPOOL_CACHE_SIZE");
 uint16_t nb_rxd = RX_DESC_DEFAULT;
 uint16_t nb_txd = TX_DESC_DEFAULT;
-uint32_t nb_pkt_per_burst = DEFAULT_PKT_BURST;
+uint32_t rx_pkt_burst = DEFAULT_PKT_BURST;
+uint32_t tx_pkt_burst = DEFAULT_PKT_BURST;
 uint32_t mb_mempool_cache_size = MEMPOOL_CACHE_SIZE;
 
 /**< Ports set in promiscuous mode off by default. */
@@ -399,7 +400,8 @@  print_usage(const char *prgname)
 		" --config (port,queue,lcore)[,(port,queue,lcore)]"
 		" [--rx-queue-size NPKTS]"
 		" [--tx-queue-size NPKTS]"
-		" [--burst NPKTS]"
+		" [--rx-burst NPKTS]"
+		" [--tx-burst NPKTS]"
 		" [--mbcache CACHESZ]"
 		" [--eth-dest=X,MM:MM:MM:MM:MM:MM]"
 		" [--max-pkt-len PKTLEN]"
@@ -426,8 +428,10 @@  print_usage(const char *prgname)
 		"            Default: %d\n"
 		"  --tx-queue-size NPKTS: Tx queue size in decimal\n"
 		"            Default: %d\n"
-		"  --burst NPKTS: Burst size in decimal\n"
-		"            Default: %d\n"
+		"  --rx-burst NPKTS: RX Burst size in decimal\n"
+		"            Default: %d, Maximum: %d\n"
+		"  --tx-burst NPKTS: TX Burst size in decimal\n"
+		"            Default: %d, Maximum: %d\n"
 		"  --mbcache CACHESZ: Mbuf cache size in decimal\n"
 		"            Default: %d\n"
 		"  --eth-dest=X,MM:MM:MM:MM:MM:MM: Ethernet destination for port X\n"
@@ -459,7 +463,10 @@  print_usage(const char *prgname)
 		"                    another is route entry at while line leads with character '%c'.\n"
 		"  --rule_ipv6=FILE: Specify the ipv6 rules entries file.\n"
 		"  --alg: ACL classify method to use, one of: %s.\n\n",
-		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT, DEFAULT_PKT_BURST, MEMPOOL_CACHE_SIZE,
+		prgname, RX_DESC_DEFAULT, TX_DESC_DEFAULT,
+		DEFAULT_PKT_BURST, MAX_PKT_BURST,
+		DEFAULT_PKT_BURST, MAX_PKT_BURST,
+		MEMPOOL_CACHE_SIZE,
 		ACL_LEAD_CHAR, ROUTE_LEAD_CHAR, alg);
 }
 
@@ -693,47 +700,30 @@  parse_mbcache_size(const char *optarg)
 			 RTE_MEMPOOL_CACHE_MAX_SIZE);
 }
 
-static void
-parse_pkt_burst(const char *optarg)
+static int
+parse_pkt_burst(const char *optarg, bool is_rx)
 {
-	struct rte_eth_dev_info dev_info;
 	unsigned long pkt_burst;
-	uint16_t burst_size;
 	char *end = NULL;
-	int ret;
 
 	/* parse decimal string */
 	pkt_burst = strtoul(optarg, &end, 10);
-	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0'))
-		return;
-
-	if (pkt_burst > MAX_PKT_BURST) {
-		RTE_LOG(INFO, L3FWD, "User provided burst must be <= %d. Using default value %d\n",
-			MAX_PKT_BURST, nb_pkt_per_burst);
-		return;
-	} else if (pkt_burst > 0) {
-		nb_pkt_per_burst = (uint32_t)pkt_burst;
-		return;
+	if ((optarg[0] == '\0') || (end == NULL) || (*end != '\0')) {
+		RTE_LOG(ERR, L3FWD, "Invalid %s-burst\n", is_rx ? "rx" : "tx");
+		return -1;
 	}
 
-	/* If user gives a value of zero, query the PMD for its recommended Rx burst size. */
-	ret = rte_eth_dev_info_get(0, &dev_info);
-	if (ret != 0)
-		return;
-	burst_size = dev_info.default_rxportconf.burst_size;
-	if (burst_size == 0) {
-		RTE_LOG(INFO, L3FWD, "PMD does not recommend a burst size. Using default value %d. "
-			"User provided value must be in [1, %d]\n",
-			nb_pkt_per_burst, MAX_PKT_BURST);
-		return;
-	} else if (burst_size > MAX_PKT_BURST) {
-		RTE_LOG(INFO, L3FWD, "PMD recommended burst size %d exceeds maximum value %d. "
-			"Using default value %d\n",
-			burst_size, MAX_PKT_BURST, nb_pkt_per_burst);
-		return;
+	if (pkt_burst > MAX_PKT_BURST || pkt_burst == 0) {
+		RTE_LOG(ERR, L3FWD, "User-provided %s burst must be in (0, %d].\n",
+			is_rx ? "Rx" : "Tx", MAX_PKT_BURST);
+		return -1;
+	} else if (pkt_burst > 0) {
+		if (is_rx)
+			rx_pkt_burst = (uint16_t)pkt_burst;
+		else
+			tx_pkt_burst = (uint16_t)pkt_burst;
 	}
-	nb_pkt_per_burst = burst_size;
-	RTE_LOG(INFO, L3FWD, "Using PMD-provided burst value %d\n", burst_size);
+	return 0;
 }
 
 #define MAX_JUMBO_PKT_LEN  9600
@@ -767,7 +757,8 @@  static const char short_options[] =
 #define CMD_LINE_OPT_RULE_IPV4 "rule_ipv4"
 #define CMD_LINE_OPT_RULE_IPV6 "rule_ipv6"
 #define CMD_LINE_OPT_ALG "alg"
-#define CMD_LINE_OPT_PKT_BURST "burst"
+#define CMD_LINE_OPT_PKT_RX_BURST "rx-burst"
+#define CMD_LINE_OPT_PKT_TX_BURST "tx-burst"
 #define CMD_LINE_OPT_MB_CACHE_SIZE "mbcache"
 
 enum {
@@ -798,7 +789,8 @@  enum {
 	CMD_LINE_OPT_ENABLE_VECTOR_NUM,
 	CMD_LINE_OPT_VECTOR_SIZE_NUM,
 	CMD_LINE_OPT_VECTOR_TMO_NS_NUM,
-	CMD_LINE_OPT_PKT_BURST_NUM,
+	CMD_LINE_OPT_RX_PKT_BURST_NUM,
+	CMD_LINE_OPT_TX_PKT_BURST_NUM,
 	CMD_LINE_OPT_MB_CACHE_SIZE_NUM,
 };
 
@@ -826,7 +818,8 @@  static const struct option lgopts[] = {
 	{CMD_LINE_OPT_RULE_IPV4,   1, 0, CMD_LINE_OPT_RULE_IPV4_NUM},
 	{CMD_LINE_OPT_RULE_IPV6,   1, 0, CMD_LINE_OPT_RULE_IPV6_NUM},
 	{CMD_LINE_OPT_ALG,   1, 0, CMD_LINE_OPT_ALG_NUM},
-	{CMD_LINE_OPT_PKT_BURST,   1, 0, CMD_LINE_OPT_PKT_BURST_NUM},
+	{CMD_LINE_OPT_PKT_RX_BURST,   1, 0, CMD_LINE_OPT_RX_PKT_BURST_NUM},
+	{CMD_LINE_OPT_PKT_TX_BURST,   1, 0, CMD_LINE_OPT_TX_PKT_BURST_NUM},
 	{CMD_LINE_OPT_MB_CACHE_SIZE,   1, 0, CMD_LINE_OPT_MB_CACHE_SIZE_NUM},
 	{NULL, 0, 0, 0}
 };
@@ -916,8 +909,20 @@  parse_args(int argc, char **argv)
 			parse_queue_size(optarg, &nb_txd, 0);
 			break;
 
-		case CMD_LINE_OPT_PKT_BURST_NUM:
-			parse_pkt_burst(optarg);
+		case CMD_LINE_OPT_TX_PKT_BURST_NUM:
+			ret = parse_pkt_burst(optarg, false);
+			if (ret) {
+				print_usage(prgname);
+				return -1;
+			}
+			break;
+
+		case CMD_LINE_OPT_RX_PKT_BURST_NUM:
+			ret = parse_pkt_burst(optarg, true);
+			if (ret) {
+				print_usage(prgname);
+				return -1;
+			}
 			break;
 
 		case CMD_LINE_OPT_MB_CACHE_SIZE_NUM: