Re: [dpdk-dev] [PATCH 3/3] l3fwd-power: add interrupt-only mode

[Harman Kalra <hkalra@marvell.com>]

On Thu, May 28, 2020 at 10:13:51AM +0100, Anatoly Burakov wrote:
> In addition to existing modes, add a mode which is very similar to
> legacy mode, but does not do frequency scaling, and thus does not
> depend on the power library.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> ---
>  examples/l3fwd-power/main.c | 215 +++++++++++++++++++++++++++++++++---
>  1 file changed, 202 insertions(+), 13 deletions(-)
> 
> diff --git a/examples/l3fwd-power/main.c b/examples/l3fwd-power/main.c
> index 5cee9d5387..4161e01974 100644
> --- a/examples/l3fwd-power/main.c
> +++ b/examples/l3fwd-power/main.c
> @@ -195,9 +195,11 @@ static int parse_ptype; /**< Parse packet type using rx callback, and */
>  			/**< disabled by default */
>  
>  enum appmode {
> -	APP_MODE_LEGACY = 0,
> +	APP_MODE_DEFAULT = 0,
> +	APP_MODE_LEGACY,
>  	APP_MODE_EMPTY_POLL,
> -	APP_MODE_TELEMETRY
> +	APP_MODE_TELEMETRY,
> +	APP_MODE_INTERRUPT
>  };
>  
>  enum appmode app_mode;
> @@ -900,6 +902,170 @@ static int event_register(struct lcore_conf *qconf)
>  
>  	return 0;
>  }
> +
> +/* main processing loop */
> +static int main_intr_loop(__rte_unused void *dummy)
> +{
> +	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
> +	unsigned int lcore_id;
> +	uint64_t prev_tsc, diff_tsc, cur_tsc;
> +	int i, j, nb_rx;
> +	uint8_t queueid;
> +	uint16_t portid;
> +	struct lcore_conf *qconf;
> +	struct lcore_rx_queue *rx_queue;
> +	uint32_t lcore_rx_idle_count = 0;
> +	uint32_t lcore_idle_hint = 0;
> +	int intr_en = 0;
> +
> +	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) /
> +				   US_PER_S * BURST_TX_DRAIN_US;
> +
> +	prev_tsc = 0;
> +
> +	lcore_id = rte_lcore_id();
> +	qconf = &lcore_conf[lcore_id];
> +
> +	if (qconf->n_rx_queue == 0) {
> +		RTE_LOG(INFO, L3FWD_POWER, "lcore %u has nothing to do\n",
> +				lcore_id);
> +		return 0;
> +	}
> +
> +	RTE_LOG(INFO, L3FWD_POWER, "entering main interrupt loop on lcore %u\n",
> +			lcore_id);
> +
> +	for (i = 0; i < qconf->n_rx_queue; i++) {
> +		portid = qconf->rx_queue_list[i].port_id;
> +		queueid = qconf->rx_queue_list[i].queue_id;
> +		RTE_LOG(INFO, L3FWD_POWER,
> +				" -- lcoreid=%u portid=%u rxqueueid=%hhu\n",
> +				lcore_id, portid, queueid);
> +	}
> +
> +	/* add into event wait list */
> +	if (event_register(qconf) == 0)
> +		intr_en = 1;
> +	else
> +		RTE_LOG(INFO, L3FWD_POWER, "RX interrupt won't enable.\n");
> +
> +	while (!is_done()) {
> +		stats[lcore_id].nb_iteration_looped++;
> +
> +		cur_tsc = rte_rdtsc();
> +
> +		/*
> +		 * TX burst queue drain
> +		 */
> +		diff_tsc = cur_tsc - prev_tsc;
> +		if (unlikely(diff_tsc > drain_tsc)) {
> +			for (i = 0; i < qconf->n_tx_port; ++i) {
> +				portid = qconf->tx_port_id[i];
> +				rte_eth_tx_buffer_flush(portid,
> +						qconf->tx_queue_id[portid],
> +						qconf->tx_buffer[portid]);
> +			}
> +			prev_tsc = cur_tsc;
> +		}
> +
> +start_rx:
> +		/*
> +		 * Read packet from RX queues
> +		 */
> +		lcore_rx_idle_count = 0;
> +		for (i = 0; i < qconf->n_rx_queue; ++i) {
> +			rx_queue = &(qconf->rx_queue_list[i]);
> +			rx_queue->idle_hint = 0;
> +			portid = rx_queue->port_id;
> +			queueid = rx_queue->queue_id;
> +
> +			nb_rx = rte_eth_rx_burst(portid, queueid, pkts_burst,
> +					MAX_PKT_BURST);
> +
> +			stats[lcore_id].nb_rx_processed += nb_rx;
> +			if (unlikely(nb_rx == 0)) {
> +				/**
> +				 * no packet received from rx queue, try to
> +				 * sleep for a while forcing CPU enter deeper
> +				 * C states.
> +				 */
> +				rx_queue->zero_rx_packet_count++;
> +
> +				if (rx_queue->zero_rx_packet_count <=
> +						MIN_ZERO_POLL_COUNT)
> +					continue;
> +
> +				rx_queue->idle_hint = power_idle_heuristic(
> +						rx_queue->zero_rx_packet_count);
> +				lcore_rx_idle_count++;
> +			} else {
> +				rx_queue->zero_rx_packet_count = 0;
> +			}
> +
> +			/* Prefetch first packets */
> +			for (j = 0; j < PREFETCH_OFFSET && j < nb_rx; j++) {
> +				rte_prefetch0(rte_pktmbuf_mtod(
> +						pkts_burst[j], void *));
> +			}
> +
> +			/* Prefetch and forward already prefetched packets */
> +			for (j = 0; j < (nb_rx - PREFETCH_OFFSET); j++) {
> +				rte_prefetch0(rte_pktmbuf_mtod(
> +						pkts_burst[j + PREFETCH_OFFSET],
> +						void *));
> +				l3fwd_simple_forward(
> +						pkts_burst[j], portid, qconf);
> +			}
> +
> +			/* Forward remaining prefetched packets */
> +			for (; j < nb_rx; j++) {
> +				l3fwd_simple_forward(
> +						pkts_burst[j], portid, qconf);
> +			}
> +		}
> +
> +		if (unlikely(lcore_rx_idle_count == qconf->n_rx_queue)) {
> +			/**
> +			 * All Rx queues empty in recent consecutive polls,
> +			 * sleep in a conservative manner, meaning sleep as
> +			 * less as possible.
> +			 */
> +			for (i = 1,
> +			    lcore_idle_hint = qconf->rx_queue_list[0].idle_hint;
> +					i < qconf->n_rx_queue; ++i) {
> +				rx_queue = &(qconf->rx_queue_list[i]);
> +				if (rx_queue->idle_hint < lcore_idle_hint)
> +					lcore_idle_hint = rx_queue->idle_hint;
> +			}
> +
> +			if (lcore_idle_hint < SUSPEND_THRESHOLD)
> +				/**
> +				 * execute "pause" instruction to avoid context
> +				 * switch which generally take hundred of
> +				 * microseconds for short sleep.
> +				 */
> +				rte_delay_us(lcore_idle_hint);
> +			else {
> +				/* suspend until rx interrupt triggers */
> +				if (intr_en) {
> +					turn_on_off_intr(qconf, 1);
> +					sleep_until_rx_interrupt(
> +							qconf->n_rx_queue);
> +					turn_on_off_intr(qconf, 0);
> +					/**
> +					 * start receiving packets immediately
> +					 */
> +					if (likely(!is_done()))
> +						goto start_rx;
> +				}
> +			}
> +			stats[lcore_id].sleep_time += lcore_idle_hint;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  /* main processing loop */
>  static int
>  main_telemetry_loop(__rte_unused void *dummy)
> @@ -1126,7 +1292,7 @@ main_empty_poll_loop(__rte_unused void *dummy)
>  }
>  /* main processing loop */
>  static int
> -main_loop(__rte_unused void *dummy)
> +main_legacy_loop(__rte_unused void *dummy)
>  {
>  	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
>  	unsigned lcore_id;
> @@ -1438,7 +1604,8 @@ print_usage(const char *prgname)
>  		"  --empty-poll: enable empty poll detection"
>  		" follow (training_flag, high_threshold, med_threshold)\n"
>  		" --telemetry: enable telemetry mode, to update"
> -		" empty polls, full polls, and core busyness to telemetry\n",
> +		" empty polls, full polls, and core busyness to telemetry\n"
> +		" --interrupt-only: enable interrupt-only mode\n",
>  		prgname);
>  }
>  
> @@ -1582,6 +1749,7 @@ parse_ep_config(const char *q_arg)
>  }
>  #define CMD_LINE_OPT_PARSE_PTYPE "parse-ptype"
>  #define CMD_LINE_OPT_TELEMETRY "telemetry"
> +#define CMD_LINE_OPT_INTERRUPT_ONLY "interrupt-only"
>  
>  /* Parse the argument given in the command line of the application */
>  static int
> @@ -1601,6 +1769,7 @@ parse_args(int argc, char **argv)
>  		{"empty-poll", 1, 0, 0},
>  		{CMD_LINE_OPT_PARSE_PTYPE, 0, 0, 0},
>  		{CMD_LINE_OPT_TELEMETRY, 0, 0, 0},
> +		{CMD_LINE_OPT_INTERRUPT_ONLY, 0, 0, 0},
>  		{NULL, 0, 0, 0}
>  	};
>  
> @@ -1674,8 +1843,8 @@ parse_args(int argc, char **argv)
>  
>  			if (!strncmp(lgopts[option_index].name,
>  						"empty-poll", 10)) {
> -				if (app_mode == APP_MODE_TELEMETRY) {
> -					printf(" empty-poll cannot be enabled as telemetry mode is enabled\n");
> +				if (app_mode != APP_MODE_DEFAULT) {
> +					printf(" empty-poll mode is mutually exclusive with other modes\n");
>  					return -1;
>  				}
>  				app_mode = APP_MODE_EMPTY_POLL;
> @@ -1692,14 +1861,25 @@ parse_args(int argc, char **argv)
>  			if (!strncmp(lgopts[option_index].name,
>  					CMD_LINE_OPT_TELEMETRY,
>  					sizeof(CMD_LINE_OPT_TELEMETRY))) {
> -				if (app_mode == APP_MODE_EMPTY_POLL) {
> -					printf("telemetry mode cannot be enabled as empty poll mode is enabled\n");
> +				if (app_mode != APP_MODE_DEFAULT) {
> +					printf(" telemetry mode is mutually exclusive with other modes\n");
>  					return -1;
>  				}
>  				app_mode = APP_MODE_TELEMETRY;
>  				printf("telemetry mode is enabled\n");
>  			}
>  
> +			if (!strncmp(lgopts[option_index].name,
> +					CMD_LINE_OPT_INTERRUPT_ONLY,
> +					sizeof(CMD_LINE_OPT_INTERRUPT_ONLY))) {
> +				if (app_mode != APP_MODE_DEFAULT) {
> +					printf(" interrupt-only mode is mutually exclusive with other modes\n");
> +					return -1;
> +				}
> +				app_mode = APP_MODE_INTERRUPT;
> +				printf("interrupt-only mode is enabled\n");
> +			}
> +
>  			if (!strncmp(lgopts[option_index].name,
>  					"enable-jumbo", 12)) {
>  				struct option lenopts =
> @@ -2253,7 +2433,12 @@ main(int argc, char **argv)
>  	if (ret < 0)
>  		rte_exit(EXIT_FAILURE, "Invalid L3FWD parameters\n");
>  
> -	if (app_mode != APP_MODE_TELEMETRY && init_power_library())
> +	if (app_mode == APP_MODE_DEFAULT)
> +		app_mode = APP_MODE_LEGACY;
> +
> +	/* only legacy and empty poll mode rely on power library */
> +	if ((app_mode == APP_MODE_LEGACY || app_mode == APP_MODE_EMPTY_POLL) &&
> +			init_power_library())
>  		rte_exit(EXIT_FAILURE, "init_power_library failed\n");
>  
Hi,

Rather than just exiting from here can we have a else condition to
automatically enter into the "interrupt only" mode.
Please correct me if I am missing something.

Thanks
Harman
	
>  	if (update_lcore_params() < 0)
> @@ -2277,7 +2462,8 @@ main(int argc, char **argv)
>  	RTE_ETH_FOREACH_DEV(portid) {
>  		struct rte_eth_conf local_port_conf = port_conf;
>  		/* not all app modes need interrupts */
> -		bool need_intr = app_mode == APP_MODE_LEGACY;
> +		bool need_intr = app_mode == APP_MODE_LEGACY ||
> +				app_mode == APP_MODE_INTERRUPT;
>  
>  		/* skip ports that are not enabled */
>  		if ((enabled_port_mask & (1 << portid)) == 0) {
> @@ -2526,12 +2712,12 @@ main(int argc, char **argv)
>  
>  	/* launch per-lcore init on every lcore */
>  	if (app_mode == APP_MODE_LEGACY) {
> -		rte_eal_mp_remote_launch(main_loop, NULL, CALL_MASTER);
> +		rte_eal_mp_remote_launch(main_legacy_loop, NULL, CALL_MASTER);
>  	} else if (app_mode == APP_MODE_EMPTY_POLL) {
>  		empty_poll_stop = false;
>  		rte_eal_mp_remote_launch(main_empty_poll_loop, NULL,
>  				SKIP_MASTER);
> -	} else {
> +	} else if (app_mode == APP_MODE_TELEMETRY) {
>  		unsigned int i;
>  
>  		/* Init metrics library */
> @@ -2555,6 +2741,8 @@ main(int argc, char **argv)
>  				"Returns global power stats. Parameters: None");
>  		rte_eal_mp_remote_launch(main_telemetry_loop, NULL,
>  						SKIP_MASTER);
> +	} else if (app_mode == APP_MODE_INTERRUPT) {
> +		rte_eal_mp_remote_launch(main_intr_loop, NULL, CALL_MASTER);
>  	}
>  
>  	if (app_mode == APP_MODE_EMPTY_POLL || app_mode == APP_MODE_TELEMETRY)
> @@ -2577,7 +2765,8 @@ main(int argc, char **argv)
>  	if (app_mode == APP_MODE_EMPTY_POLL)
>  		rte_power_empty_poll_stat_free();
>  
> -	if (app_mode != APP_MODE_TELEMETRY && deinit_power_library())
> +	if ((app_mode == APP_MODE_LEGACY || app_mode == APP_MODE_EMPTY_POLL) &&
> +			deinit_power_library())
>  		rte_exit(EXIT_FAILURE, "deinit_power_library failed\n");
>  
>  	if (rte_eal_cleanup() < 0)
> -- 
> 2.17.1