[dpdk-dev] [PATCH 1/2] net/netvsc: allow setting rx and tx copy break

[Long Li <longli@linuxonhyperv.com>]

From: Stephen Hemminger <stephen@networkplumber.org>

The values for Rx and Tx copy break should be tunable rather
than hard coded constants.

The rx_copybreak sets the threshold where the driver uses an
external mbuf to avoid having to copy data. Setting 0 for copybreak
will cause driver to always create an external mbuf. Setting
a value greater than the MTU would prevent it from ever making
an external mbuf and always copy. The default value is 256 (bytes).

Likewise the tx_copybreak sets the threshold where the driver
aggregates multiple small packets into one request. If tx_copybreak
is 0 then each packet goes as a VMBus request (no copying).
If tx_copybreak is set larger than the MTU, then all packets smaller
than the chunk size of the VMBus send buffer will be copied; larger
packets always have to go as a single direct request. The default
value is 512 (bytes).

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/net/netvsc/hn_ethdev.c | 63 +++++++++++++++++++---------------
 drivers/net/netvsc/hn_rxtx.c   |  7 ++--
 drivers/net/netvsc/hn_var.h    |  5 +++
 3 files changed, 43 insertions(+), 32 deletions(-)

diff --git a/drivers/net/netvsc/hn_ethdev.c b/drivers/net/netvsc/hn_ethdev.c
index 4a01f1d464..e4f13b962c 100644
--- a/drivers/net/netvsc/hn_ethdev.c
+++ b/drivers/net/netvsc/hn_ethdev.c
@@ -45,6 +45,10 @@
 			    DEV_RX_OFFLOAD_VLAN_STRIP | \
 			    DEV_RX_OFFLOAD_RSS_HASH)
 
+#define NETVSC_ARG_LATENCY "latency"
+#define NETVSC_ARG_RXBREAK "rx_copybreak"
+#define NETVSC_ARG_TXBREAK "tx_copybreak"
+
 struct hn_xstats_name_off {
 	char name[RTE_ETH_XSTATS_NAME_SIZE];
 	unsigned int offset;
@@ -136,38 +140,20 @@ eth_dev_vmbus_release(struct rte_eth_dev *eth_dev)
 	eth_dev->intr_handle = NULL;
 }
 
-/* handle "latency=X" from devargs */
-static int hn_set_latency(const char *key, const char *value, void *opaque)
-{
-	struct hn_data *hv = opaque;
-	char *endp = NULL;
-	unsigned long lat;
-
-	errno = 0;
-	lat = strtoul(value, &endp, 0);
-
-	if (*value == '\0' || *endp != '\0') {
-		PMD_DRV_LOG(ERR, "invalid parameter %s=%s", key, value);
-		return -EINVAL;
-	}
-
-	PMD_DRV_LOG(DEBUG, "set latency %lu usec", lat);
-
-	hv->latency = lat * 1000;	/* usec to nsec */
-	return 0;
-}
-
 /* Parse device arguments */
 static int hn_parse_args(const struct rte_eth_dev *dev)
 {
 	struct hn_data *hv = dev->data->dev_private;
 	struct rte_devargs *devargs = dev->device->devargs;
 	static const char * const valid_keys[] = {
-		"latency",
+		NETVSC_ARG_LATENCY,
+		NETVSC_ARG_RXBREAK,
+		NETVSC_ARG_TXBREAK,
 		NULL
 	};
+	int latency = -1, rx_break = -1, tx_break = -1;
 	struct rte_kvargs *kvlist;
-	int ret;
+	unsigned int i;
 
 	if (!devargs)
 		return 0;
@@ -181,12 +167,32 @@ static int hn_parse_args(const struct rte_eth_dev *dev)
 		return -EINVAL;
 	}
 
-	ret = rte_kvargs_process(kvlist, "latency", hn_set_latency, hv);
-	if (ret)
-		PMD_DRV_LOG(ERR, "Unable to process latency arg\n");
+	for (i = 0; i != kvlist->count; ++i) {
+		const struct rte_kvargs_pair *pair = &kvlist->pairs[i];
+
+		if (!strcmp(pair->key, NETVSC_ARG_LATENCY))
+			latency = atoi(pair->value);
+		else if (!strcmp(pair->key, NETVSC_ARG_RXBREAK))
+			rx_break = atoi(pair->value);
+		else if (!strcmp(pair->key, NETVSC_ARG_TXBREAK))
+			tx_break = atoi(pair->value);
+	}
+
+	if (latency >= 0) {
+		PMD_DRV_LOG(DEBUG, "set latency %d usec", latency);
+		hv->latency = latency * 1000;	/* usec to nsec */
+	}
+	if (rx_break >= 0) {
+		PMD_DRV_LOG(DEBUG, "rx copy break set to %d", rx_break);
+		hv->rx_copybreak = rx_break;
+	}
+	if (tx_break >= 0) {
+		PMD_DRV_LOG(DEBUG, "tx copy break set to %d", tx_break);
+		hv->tx_copybreak = tx_break;
+	}
 
 	rte_kvargs_free(kvlist);
-	return ret;
+	return 0;
 }
 
 /* Update link status.
@@ -966,7 +972,10 @@ eth_hn_dev_init(struct rte_eth_dev *eth_dev)
 	hv->chim_res  = &vmbus->resource[HV_SEND_BUF_MAP];
 	hv->port_id = eth_dev->data->port_id;
 	hv->latency = HN_CHAN_LATENCY_NS;
+	hv->rx_copybreak = HN_RXCOPY_THRESHOLD;
+	hv->tx_copybreak = HN_TXCOPY_THRESHOLD;
 	hv->max_queues = 1;
+
 	rte_rwlock_init(&hv->vf_lock);
 	hv->vf_port = HN_INVALID_PORT;
 
diff --git a/drivers/net/netvsc/hn_rxtx.c b/drivers/net/netvsc/hn_rxtx.c
index 5d59db513c..b62c0b0181 100644
--- a/drivers/net/netvsc/hn_rxtx.c
+++ b/drivers/net/netvsc/hn_rxtx.c
@@ -40,9 +40,6 @@
 	(sizeof(struct vmbus_chanpkt_hdr) + sizeof(struct hn_nvs_rndis))
 
 #define HN_TXD_CACHE_SIZE	32 /* per cpu tx_descriptor pool cache */
-#define HN_TXCOPY_THRESHOLD	512
-
-#define HN_RXCOPY_THRESHOLD	256
 #define HN_RXQ_EVENT_DEFAULT	2048
 
 struct hn_rxinfo {
@@ -568,7 +565,7 @@ static void hn_rxpkt(struct hn_rx_queue *rxq, struct hn_rx_bufinfo *rxb,
 	 * For large packets, avoid copy if possible but need to keep
 	 * some space available in receive area for later packets.
 	 */
-	if (dlen >= HN_RXCOPY_THRESHOLD &&
+	if (dlen > hv->rx_copybreak &&
 	    (uint32_t)rte_atomic32_read(&rxq->rxbuf_outstanding) <
 			hv->rxbuf_section_cnt / 2) {
 		struct rte_mbuf_ext_shared_info *shinfo;
@@ -1516,7 +1513,7 @@ hn_xmit_pkts(void *ptxq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			break;
 
 		/* For small packets aggregate them in chimney buffer */
-		if (m->pkt_len < HN_TXCOPY_THRESHOLD && pkt_size <= txq->agg_szmax) {
+		if (m->pkt_len <= hv->tx_copybreak && pkt_size <= txq->agg_szmax) {
 			/* If this packet will not fit, then flush  */
 			if (txq->agg_pktleft == 0 ||
 			    RTE_ALIGN(pkt_size, txq->agg_align) > txq->agg_szleft) {
diff --git a/drivers/net/netvsc/hn_var.h b/drivers/net/netvsc/hn_var.h
index 56bfa972d1..c1bdafb413 100644
--- a/drivers/net/netvsc/hn_var.h
+++ b/drivers/net/netvsc/hn_var.h
@@ -23,6 +23,9 @@
 /* Host monitor interval */
 #define HN_CHAN_LATENCY_NS	50000
 
+#define HN_TXCOPY_THRESHOLD	512
+#define HN_RXCOPY_THRESHOLD	256
+
 /* Buffers need to be aligned */
 #ifndef PAGE_SIZE
 #define PAGE_SIZE 4096
@@ -114,6 +117,7 @@ struct hn_data {
 
 	struct rte_mem_resource *rxbuf_res;	/* UIO resource for Rx */
 	uint32_t	rxbuf_section_cnt;	/* # of Rx sections */
+	uint32_t	rx_copybreak;
 	uint16_t	max_queues;		/* Max available queues */
 	uint16_t	num_queues;
 	uint64_t	rss_offloads;
@@ -122,6 +126,7 @@ struct hn_data {
 	struct rte_mem_resource *chim_res;	/* UIO resource for Tx */
 	struct rte_bitmap *chim_bmap;		/* Send buffer map */
 	void		*chim_bmem;
+	uint32_t	tx_copybreak;
 	uint32_t	chim_szmax;		/* Max size per buffer */
 	uint32_t	chim_cnt;		/* Max packets per buffer */
 
-- 
2.25.1