[PATCH v4 08/10] ethdev: add getter for per-queue Tx rate limit

[Slava Ovsiienko]

Acked-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>

> -----Original Message-----
> From: Vincent Jardin <vjardin at free.fr>
> Sent: Sunday, March 22, 2026 3:46 PM
> To: dev at dpdk.org
> Cc: Raslan Darawsheh <rasland at nvidia.com>; NBU-Contact-Thomas Monjalon
> (EXTERNAL) <thomas at monjalon.net>; andrew.rybchenko at oktetlabs.ru;
> Dariusz Sosnowski <dsosnowski at nvidia.com>; Slava Ovsiienko
> <viacheslavo at nvidia.com>; Bing Zhao <bingz at nvidia.com>; Ori Kam
> <orika at nvidia.com>; Suanming Mou <suanmingm at nvidia.com>; Matan Azrad
> <matan at nvidia.com>; stephen at networkplumber.org;
> aman.deep.singh at intel.com; Vincent Jardin <vjardin at free.fr>
> Subject: [PATCH v4 08/10] ethdev: add getter for per-queue Tx rate limit
> 
> The existing rte_eth_set_queue_rate_limit() API allows setting a per-queue Tx
> rate but provides no way to read it back. Applications such as grout are forced
> to maintain a shadow copy of the rate to be able to report it.
> 
> Add rte_eth_get_queue_rate_limit() as the symmetric getter, following the
> established DPDK pattern (e.g. rte_eth_dev_set_mtu/get_mtu,
> rte_eth_dev_set_vlan_offload/get_vlan_offload).
> 
> This adds:
> - eth_get_queue_rate_limit_t driver callback in ethdev_driver.h
> - rte_eth_get_queue_rate_limit() public experimental API (26.07)
> - Trace point matching the existing setter pattern
> - Generic testpmd command: show port <id> queue <id> rate
> 
> Signed-off-by: Vincent Jardin <vjardin at free.fr>
> ---
>  app/test-pmd/cmdline.c           | 69 ++++++++++++++++++++++++++++++++
>  lib/ethdev/ethdev_driver.h       |  7 ++++
>  lib/ethdev/ethdev_trace.h        |  9 +++++
>  lib/ethdev/ethdev_trace_points.c |  3 ++
>  lib/ethdev/rte_ethdev.c          | 35 ++++++++++++++++
>  lib/ethdev/rte_ethdev.h          | 24 +++++++++++
>  6 files changed, 147 insertions(+)
> 
> diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c index
> c5abeb5730..cc9c462498 100644
> --- a/app/test-pmd/cmdline.c
> +++ b/app/test-pmd/cmdline.c
> @@ -8982,6 +8982,74 @@ static cmdline_parse_inst_t cmd_queue_rate_limit
> = {
>  	},
>  };
> 
> +/* *** SHOW RATE LIMIT FOR A QUEUE OF A PORT *** */ struct
> +cmd_show_queue_rate_limit_result {
> +	cmdline_fixed_string_t show;
> +	cmdline_fixed_string_t port;
> +	uint16_t port_num;
> +	cmdline_fixed_string_t queue;
> +	uint16_t queue_num;
> +	cmdline_fixed_string_t rate;
> +};
> +
> +static void cmd_show_queue_rate_limit_parsed(void *parsed_result,
> +		__rte_unused struct cmdline *cl,
> +		__rte_unused void *data)
> +{
> +	struct cmd_show_queue_rate_limit_result *res = parsed_result;
> +	uint32_t tx_rate = 0;
> +	int ret;
> +
> +	ret = rte_eth_get_queue_rate_limit(res->port_num, res->queue_num,
> +					   &tx_rate);
> +	if (ret) {
> +		fprintf(stderr, "Get queue rate limit failed: %s\n",
> +			rte_strerror(-ret));
> +		return;
> +	}
> +	if (tx_rate)
> +		printf("Port %u Queue %u rate limit: %u Mbps\n",
> +		       res->port_num, res->queue_num, tx_rate);
> +	else
> +		printf("Port %u Queue %u rate limit: disabled\n",
> +		       res->port_num, res->queue_num); }
> +
> +static cmdline_parse_token_string_t cmd_show_queue_rate_limit_show =
> +	TOKEN_STRING_INITIALIZER(struct
> cmd_show_queue_rate_limit_result,
> +				show, "show");
> +static cmdline_parse_token_string_t cmd_show_queue_rate_limit_port =
> +	TOKEN_STRING_INITIALIZER(struct
> cmd_show_queue_rate_limit_result,
> +				port, "port");
> +static cmdline_parse_token_num_t cmd_show_queue_rate_limit_portnum =
> +	TOKEN_NUM_INITIALIZER(struct cmd_show_queue_rate_limit_result,
> +				port_num, RTE_UINT16);
> +static cmdline_parse_token_string_t cmd_show_queue_rate_limit_queue =
> +	TOKEN_STRING_INITIALIZER(struct
> cmd_show_queue_rate_limit_result,
> +				queue, "queue");
> +static cmdline_parse_token_num_t cmd_show_queue_rate_limit_queuenum
> =
> +	TOKEN_NUM_INITIALIZER(struct cmd_show_queue_rate_limit_result,
> +				queue_num, RTE_UINT16);
> +static cmdline_parse_token_string_t cmd_show_queue_rate_limit_rate =
> +	TOKEN_STRING_INITIALIZER(struct
> cmd_show_queue_rate_limit_result,
> +				rate, "rate");
> +
> +static cmdline_parse_inst_t cmd_show_queue_rate_limit = {
> +	.f = cmd_show_queue_rate_limit_parsed,
> +	.data = NULL,
> +	.help_str = "show port <port_id> queue <queue_id> rate: "
> +		"Show rate limit for a queue on port_id",
> +	.tokens = {
> +		(void *)&cmd_show_queue_rate_limit_show,
> +		(void *)&cmd_show_queue_rate_limit_port,
> +		(void *)&cmd_show_queue_rate_limit_portnum,
> +		(void *)&cmd_show_queue_rate_limit_queue,
> +		(void *)&cmd_show_queue_rate_limit_queuenum,
> +		(void *)&cmd_show_queue_rate_limit_rate,
> +		NULL,
> +	},
> +};
> +
>  /* *** SET RATE LIMIT FOR A VF OF A PORT *** */  struct
> cmd_vf_rate_limit_result {
>  	cmdline_fixed_string_t set;
> @@ -14270,6 +14338,7 @@ static cmdline_parse_ctx_t builtin_ctx[] = {
>  	&cmd_set_uc_all_hash_filter,
>  	&cmd_vf_mac_addr_filter,
>  	&cmd_queue_rate_limit,
> +	&cmd_show_queue_rate_limit,
>  	&cmd_tunnel_udp_config,
>  	&cmd_showport_rss_hash,
>  	&cmd_showport_rss_hash_key,
> diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h index
> 1255cd6f2c..0f336f9567 100644
> --- a/lib/ethdev/ethdev_driver.h
> +++ b/lib/ethdev/ethdev_driver.h
> @@ -762,6 +762,11 @@ typedef int (*eth_set_queue_rate_limit_t)(struct
> rte_eth_dev *dev,
>  				uint16_t queue_idx,
>  				uint32_t tx_rate);
> 
> +/** @internal Get queue Tx rate. */
> +typedef int (*eth_get_queue_rate_limit_t)(struct rte_eth_dev *dev,
> +				uint16_t queue_idx,
> +				uint32_t *tx_rate);
> +
>  /** @internal Add tunneling UDP port. */  typedef int
> (*eth_udp_tunnel_port_add_t)(struct rte_eth_dev *dev,
>  					 struct rte_eth_udp_tunnel
> *tunnel_udp); @@ -1522,6 +1527,8 @@ struct eth_dev_ops {
> 
>  	/** Set queue rate limit */
>  	eth_set_queue_rate_limit_t set_queue_rate_limit;
> +	/** Get queue rate limit */
> +	eth_get_queue_rate_limit_t get_queue_rate_limit;
> 
>  	/** Configure RSS hash protocols and hashing key */
>  	rss_hash_update_t          rss_hash_update;
> diff --git a/lib/ethdev/ethdev_trace.h b/lib/ethdev/ethdev_trace.h index
> 482befc209..6554cc1a21 100644
> --- a/lib/ethdev/ethdev_trace.h
> +++ b/lib/ethdev/ethdev_trace.h
> @@ -908,6 +908,15 @@ RTE_TRACE_POINT(
>  	rte_trace_point_emit_int(ret);
>  )
> 
> +RTE_TRACE_POINT(
> +	rte_eth_trace_get_queue_rate_limit,
> +	RTE_TRACE_POINT_ARGS(uint16_t port_id, uint16_t queue_idx,
> +		int ret),
> +	rte_trace_point_emit_u16(port_id);
> +	rte_trace_point_emit_u16(queue_idx);
> +	rte_trace_point_emit_int(ret);
> +)
> +
>  RTE_TRACE_POINT(
>  	rte_eth_trace_rx_avail_thresh_set,
>  	RTE_TRACE_POINT_ARGS(uint16_t port_id, uint16_t queue_id, diff --
> git a/lib/ethdev/ethdev_trace_points.c b/lib/ethdev/ethdev_trace_points.c
> index 071c508327..0a28378a56 100644
> --- a/lib/ethdev/ethdev_trace_points.c
> +++ b/lib/ethdev/ethdev_trace_points.c
> @@ -347,6 +347,9 @@
> RTE_TRACE_POINT_REGISTER(rte_ethdev_trace_uc_all_hash_table_set,
>  RTE_TRACE_POINT_REGISTER(rte_eth_trace_set_queue_rate_limit,
>  	lib.ethdev.set_queue_rate_limit)
> 
> +RTE_TRACE_POINT_REGISTER(rte_eth_trace_get_queue_rate_limit,
> +	lib.ethdev.get_queue_rate_limit)
> +
>  RTE_TRACE_POINT_REGISTER(rte_eth_trace_rx_avail_thresh_set,
>  	lib.ethdev.rx_avail_thresh_set)
> 
> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c index
> 2edc7a362e..5e763e1855 100644
> --- a/lib/ethdev/rte_ethdev.c
> +++ b/lib/ethdev/rte_ethdev.c
> @@ -5694,6 +5694,41 @@ int rte_eth_set_queue_rate_limit(uint16_t
> port_id, uint16_t queue_idx,
>  	return ret;
>  }
> 
> +RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_eth_get_queue_rate_limit, 26.07)
> int
> +rte_eth_get_queue_rate_limit(uint16_t port_id, uint16_t queue_idx,
> +					uint32_t *tx_rate)
> +{
> +	struct rte_eth_dev *dev;
> +	int ret;
> +
> +	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> +	dev = &rte_eth_devices[port_id];
> +
> +	if (tx_rate == NULL) {
> +		RTE_ETHDEV_LOG_LINE(ERR,
> +			"Get queue rate limit:port %u: NULL tx_rate pointer",
> +			port_id);
> +		return -EINVAL;
> +	}
> +
> +	if (queue_idx >= dev->data->nb_tx_queues) {
> +		RTE_ETHDEV_LOG_LINE(ERR,
> +			"Get queue rate limit:port %u: invalid queue ID=%u",
> +			port_id, queue_idx);
> +		return -EINVAL;
> +	}
> +
> +	if (dev->dev_ops->get_queue_rate_limit == NULL)
> +		return -ENOTSUP;
> +	ret = eth_err(port_id,
> +		      dev->dev_ops->get_queue_rate_limit(dev, queue_idx,
> +							 tx_rate));
> +
> +	rte_eth_trace_get_queue_rate_limit(port_id, queue_idx, ret);
> +
> +	return ret;
> +}
> +
>  RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_eth_rx_avail_thresh_set, 22.07)
> int rte_eth_rx_avail_thresh_set(uint16_t port_id, uint16_t queue_id,
>  			       uint8_t avail_thresh)
> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h index
> 0d8e2d0236..e525217b77 100644
> --- a/lib/ethdev/rte_ethdev.h
> +++ b/lib/ethdev/rte_ethdev.h
> @@ -4817,6 +4817,30 @@ int rte_eth_dev_uc_all_hash_table_set(uint16_t
> port_id, uint8_t on);  int rte_eth_set_queue_rate_limit(uint16_t port_id,
> uint16_t queue_idx,
>  			uint32_t tx_rate);
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change, or be removed, without prior
> notice.
> + *
> + * Get the rate limitation for a queue on an Ethernet device.
> + *
> + * @param port_id
> + *   The port identifier of the Ethernet device.
> + * @param queue_idx
> + *   The queue ID.
> + * @param[out] tx_rate
> + *   A pointer to retrieve the Tx rate in Mbps.
> + *   0 means rate limiting is disabled.
> + * @return
> + *   - (0) if successful.
> + *   - (-ENOTSUP) if hardware doesn't support this feature.
> + *   - (-ENODEV) if *port_id* invalid.
> + *   - (-EIO) if device is removed.
> + *   - (-EINVAL) if bad parameter.
> + */
> +__rte_experimental
> +int rte_eth_get_queue_rate_limit(uint16_t port_id, uint16_t queue_idx,
> +			uint32_t *tx_rate);
> +
>  /**
>   * Configuration of Receive Side Scaling hash computation of Ethernet device.
>   *
> --
> 2.43.0