[dpdk-dev] [PATCH v2 22/32] net/sfc: support Tx free threshold

[Andrew Rybchenko <arybchenko@solarflare.com>]

From: Ivan Malov <ivan.malov@oktetlabs.ru>

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andrew Lee <alee@solarflare.com>
Reviewed-by: Robert Stonehouse <rstonehouse@solarflare.com>
---
 drivers/net/sfc/sfc_ethdev.c |  1 +
 drivers/net/sfc/sfc_tweak.h  |  3 +++
 drivers/net/sfc/sfc_tx.c     | 14 ++++++++------
 drivers/net/sfc/sfc_tx.h     | 10 +---------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/net/sfc/sfc_ethdev.c b/drivers/net/sfc/sfc_ethdev.c
index 73e8fe2..5d0d774 100644
--- a/drivers/net/sfc/sfc_ethdev.c
+++ b/drivers/net/sfc/sfc_ethdev.c
@@ -864,6 +864,7 @@ sfc_tx_queue_info_get(struct rte_eth_dev *dev, uint16_t tx_queue_id,
 	memset(qinfo, 0, sizeof(*qinfo));
 
 	qinfo->conf.txq_flags = txq_info->txq->flags;
+	qinfo->conf.tx_free_thresh = txq_info->txq->free_thresh;
 	qinfo->nb_desc = txq_info->entries;
 
 	sfc_adapter_unlock(sa);
diff --git a/drivers/net/sfc/sfc_tweak.h b/drivers/net/sfc/sfc_tweak.h
index 8a60f35..be39a5e 100644
--- a/drivers/net/sfc/sfc_tweak.h
+++ b/drivers/net/sfc/sfc_tweak.h
@@ -48,4 +48,7 @@
  */
 #define SFC_TX_XMIT_PKTS_REAP_AT_LEAST_ONCE	0
 
+/** Default free threshold follows recommendations from DPDK documentation */
+#define SFC_TX_DEFAULT_FREE_THRESH	32
+
 #endif /* _SFC_TWEAK_H_ */
diff --git a/drivers/net/sfc/sfc_tx.c b/drivers/net/sfc/sfc_tx.c
index a240610..13b24f7 100644
--- a/drivers/net/sfc/sfc_tx.c
+++ b/drivers/net/sfc/sfc_tx.c
@@ -54,7 +54,7 @@
 #define SFC_TX_QFLUSH_POLL_ATTEMPTS	(2000)
 
 static int
-sfc_tx_qcheck_conf(struct sfc_adapter *sa,
+sfc_tx_qcheck_conf(struct sfc_adapter *sa, uint16_t nb_tx_desc,
 		   const struct rte_eth_txconf *tx_conf)
 {
 	unsigned int flags = tx_conf->txq_flags;
@@ -65,9 +65,10 @@ sfc_tx_qcheck_conf(struct sfc_adapter *sa,
 		rc = EINVAL;
 	}
 
-	if (tx_conf->tx_free_thresh != 0) {
+	if (tx_conf->tx_free_thresh > EFX_TXQ_LIMIT(nb_tx_desc)) {
 		sfc_err(sa,
-			"setting explicit TX free threshold is not supported");
+			"TxQ free threshold too large: %u vs maximum %u",
+			tx_conf->tx_free_thresh, EFX_TXQ_LIMIT(nb_tx_desc));
 		rc = EINVAL;
 	}
 
@@ -147,7 +148,7 @@ sfc_tx_qinit(struct sfc_adapter *sa, unsigned int sw_index,
 
 	sfc_log_init(sa, "TxQ = %u", sw_index);
 
-	rc = sfc_tx_qcheck_conf(sa, tx_conf);
+	rc = sfc_tx_qcheck_conf(sa, nb_tx_desc, tx_conf);
 	if (rc != 0)
 		goto fail_bad_conf;
 
@@ -188,6 +189,8 @@ sfc_tx_qinit(struct sfc_adapter *sa, unsigned int sw_index,
 
 	txq->state = SFC_TXQ_INITIALIZED;
 	txq->ptr_mask = txq_info->entries - 1;
+	txq->free_thresh = (tx_conf->tx_free_thresh) ? tx_conf->tx_free_thresh :
+						     SFC_TX_DEFAULT_FREE_THRESH;
 	txq->hw_index = sw_index;
 	txq->flags = tx_conf->txq_flags;
 	txq->evq = evq;
@@ -537,8 +540,7 @@ sfc_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	unsigned int pkts_sent = 0;
 	efx_desc_t *pend = &txq->pend_desc[0];
 	const unsigned int hard_max_fill = EFX_TXQ_LIMIT(txq->ptr_mask + 1);
-	const unsigned int soft_max_fill = hard_max_fill -
-					   SFC_TX_MAX_PKT_DESC;
+	const unsigned int soft_max_fill = hard_max_fill - txq->free_thresh;
 	unsigned int fill_level = added - txq->completed;
 	boolean_t reap_done;
 	int rc __rte_unused;
diff --git a/drivers/net/sfc/sfc_tx.h b/drivers/net/sfc/sfc_tx.h
index fe2736b..f9eecc0 100644
--- a/drivers/net/sfc/sfc_tx.h
+++ b/drivers/net/sfc/sfc_tx.h
@@ -40,15 +40,6 @@ extern "C" {
 #endif
 
 /**
- * Estimated maximum number of segments that transmit packet consists of;
- * it is determined with respect to the expectation of a packet to consist
- * of a header plus a couple of data segments one of those crossing 4K page;
- * it is used by transmit path to avoid redundant reaping and, thus,
- * to avoid increase of latency
- */
-#define SFC_TX_MAX_PKT_DESC	4
-
-/**
  * A segment must not cross 4K boundary
  * (this is a requirement of NIC TX descriptors)
  */
@@ -85,6 +76,7 @@ struct sfc_txq {
 	unsigned int		added;
 	unsigned int		pending;
 	unsigned int		completed;
+	unsigned int		free_thresh;
 
 	unsigned int		hw_index;
 	unsigned int		flags;
-- 
2.5.5