On 1/11/24 18:17, jer...@marvell.com wrote:
From: Jerin Jacob <jer...@marvell.com>
Introduce a new API to retrieve the number of used descriptors
in a Tx queue. Applications can leverage this API in the fast path to
inspect the Tx queue occupancy and take appropriate actions based on the
available free descriptors.
A notable use case could be implementing Random Early Discard (RED)
in software based on Tx queue occupancy.
Signed-off-by: Jerin Jacob <jer...@marvell.com>
with few nits below
Reviewed-by: Andrew Rybchenko <andrew.rybche...@oktetlabs.ru>
[snip]
diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
index f7d9980849..0d5a8733fc 100644
--- a/doc/guides/nics/features.rst
+++ b/doc/guides/nics/features.rst
@@ -962,6 +962,16 @@ management (see :doc:`../prog_guide/power_man` for more
details).
* **[implements] eth_dev_ops**: ``get_monitor_addr``
+.. _nic_features_tx_queue_used_count:
I'd stick to shorter version _nic_features_tx_queue_count to match API
naming and feature title below.
+
+Tx queue count
+--------------
+
+Supports to get the number of used descriptors of a Tx queue.
+
+* **[implements] eth_dev_ops**: ``tx_queue_count``.
+* **[related] API**: ``rte_eth_tx_queue_count()``.
+
.. _nic_features_other:
Other dev ops not represented by a Feature
[snip]
diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
index 21e3a21903..af59da9652 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -6803,6 +6803,80 @@ rte_eth_recycle_mbufs(uint16_t rx_port_id, uint16_t
rx_queue_id,
__rte_experimental
int rte_eth_buffer_split_get_supported_hdr_ptypes(uint16_t port_id, uint32_t
*ptypes, int num);
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the number of used descriptors of a Tx queue
+ *
+ * This function retrieves the number of used descriptors of a transmit queue.
+ * Applications can use this API in the fast path to inspect Tx queue
occupancy and take
+ * appropriate actions based on the available free descriptors.
+ * An example action could be implementing the Random Early Discard (RED).
+ *
+ * Since it's a fast-path function, no check is performed on port_id and
+ * tx_queue_id. The caller must therefore ensure that the port is enabled
+ * and the queue is configured and running.
+ *
+ * @param port_id
+ * The port identifier of the device.
+ * @param tx_queue_id
+ * The index of the transmit queue.
+ * The value must be in the range [0, nb_tx_queue - 1] previously supplied
+ * to rte_eth_dev_configure().
+ * @return
+ * The number of used descriptors in the specific queue, or:
+ * - (-ENODEV) if *port_id* is invalid. Enabled only when
RTE_ETHDEV_DEBUG_TX is enabled
+ * - (-EINVAL) if *queue_id* is invalid. Enabled only when
RTE_ETHDEV_DEBUG_TX is enabled
+ * - (-ENOTSUP) if the device does not support this function.
+ *
+ * @note This function is designed for fast-path use.
+ */
+__rte_experimental
+static inline int
+rte_eth_tx_queue_count(uint16_t port_id, uint16_t tx_queue_id)
+{
+ struct rte_eth_fp_ops *fops;
+ void *qd;
+ int rc;
+
+#ifdef RTE_ETHDEV_DEBUG_TX
+ if (port_id >= RTE_MAX_ETHPORTS || !rte_eth_dev_is_valid_port(port_id))
{
+ RTE_ETHDEV_LOG_LINE(ERR, "Invalid port_id=%u", port_id);
+ rc = -ENODEV;
+ rte_eth_trace_tx_queue_count(port_id, tx_queue_id, rc);
+ return rc;
+ }
+
+ rc = -EINVAL;
Since it is a debug, IMHO it is better to keep the code simple and init
rc in two below if bodies separately rather than relying on shared init
here.
+ if (tx_queue_id >= RTE_MAX_QUEUES_PER_PORT) {
+ RTE_ETHDEV_LOG_LINE(ERR, "Invalid Tx queue_id=%u for
port_id=%u",
+ tx_queue_id, port_id);
+ rte_eth_trace_tx_queue_count(port_id, tx_queue_id, rc);
+ return rc;
+ }
+#endif
+
+ /* Fetch pointer to Tx queue data */
+ fops = &rte_eth_fp_ops[port_id];
+ qd = fops->txq.data[tx_queue_id];
+
+#ifdef RTE_ETHDEV_DEBUG_TX
+ if (qd == NULL) {
+ RTE_ETHDEV_LOG_LINE(ERR, "Invalid Tx queue_id=%u for
port_id=%u",
+ tx_queue_id, port_id);
+ rte_eth_trace_tx_queue_count(port_id, tx_queue_id, rc);
+ return rc;
+ }
+#endif
+ if (fops->tx_queue_count == NULL)
Don't we need trace here? (no strong opinion, just trying to understand
why it is missing here)
+ return -ENOTSUP;
+
+ rc = fops->tx_queue_count(qd);
+ rte_eth_trace_tx_queue_count(port_id, tx_queue_id, rc);
+
+ return rc;
+}
#ifdef __cplusplus
}
#endif
[snip]
