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

[Konstantin Ananyev <konstantin.ananyev@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
> >
> > 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: