From: Ilya Maximets Date: Mon, 27 Jun 2016 13:28:16 +0000 (+0300) Subject: netdev-dpdk: Use instant sending instead of queueing of packets. X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=b59cc14e032da370021794bfd1bdd3d67e88a9a3;p=cascardo%2Fovs.git netdev-dpdk: Use instant sending instead of queueing of packets. Current implementarion of TX packet's queueing is broken in several ways: * TX queue flushing implemented on receive assumes that all core_id-s are sequential and starts from zero. This may lead to situation when packets will stuck in queue forever and, also, this influences on latency. * For a long time flushing logic depends on uninitialized 'txq_needs_locking', because it usually calculated after 'netdev_dpdk_alloc_txq' but used inside of this function for initialization of 'flush_tx'. Testing shows no performance difference with and without queueing. Lets remove queueing at all because it doesn't work properly now and also does not increase performance. Signed-off-by: Ilya Maximets Acked-by: Daniele Di Proietto --- diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c index 02e2c58c9..8bb33d6b2 100644 --- a/lib/netdev-dpdk.c +++ b/lib/netdev-dpdk.c @@ -165,7 +165,6 @@ static const struct rte_eth_conf port_conf = { }, }; -enum { MAX_TX_QUEUE_LEN = 384 }; enum { DPDK_RING_SIZE = 256 }; BUILD_ASSERT_DECL(IS_POW2(DPDK_RING_SIZE)); enum { DRAIN_TSC = 200000ULL }; @@ -282,8 +281,7 @@ static struct ovs_list dpdk_mp_list OVS_GUARDED_BY(dpdk_mutex) = OVS_LIST_INITIALIZER(&dpdk_mp_list); /* This mutex must be used by non pmd threads when allocating or freeing - * mbufs through mempools. Since dpdk_queue_pkts() and dpdk_queue_flush() may - * use mempools, a non pmd thread should hold this mutex while calling them */ + * mbufs through mempools. */ static struct ovs_mutex nonpmd_mempool_mutex = OVS_MUTEX_INITIALIZER; struct dpdk_mp { @@ -297,17 +295,12 @@ struct dpdk_mp { /* There should be one 'struct dpdk_tx_queue' created for * each cpu core. */ struct dpdk_tx_queue { - bool flush_tx; /* Set to true to flush queue everytime */ - /* pkts are queued. */ - int count; rte_spinlock_t tx_lock; /* Protects the members and the NIC queue * from concurrent access. It is used only * if the queue is shared among different * pmd threads (see 'txq_needs_locking'). */ int map; /* Mapping of configured vhost-user queues * to enabled by guest. */ - uint64_t tsc; - struct rte_mbuf *burst_pkts[MAX_TX_QUEUE_LEN]; }; /* dpdk has no way to remove dpdk ring ethernet devices @@ -720,19 +713,6 @@ netdev_dpdk_alloc_txq(struct netdev_dpdk *dev, unsigned int n_txqs) dev->tx_q = dpdk_rte_mzalloc(n_txqs * sizeof *dev->tx_q); for (i = 0; i < n_txqs; i++) { - int numa_id = ovs_numa_get_numa_id(i); - - if (!dev->txq_needs_locking) { - /* Each index is considered as a cpu core id, since there should - * be one tx queue for each cpu core. If the corresponding core - * is not on the same numa node as 'dev', flags the - * 'flush_tx'. */ - dev->tx_q[i].flush_tx = dev->socket_id == numa_id; - } else { - /* Queues are shared among CPUs. Always flush */ - dev->tx_q[i].flush_tx = true; - } - /* Initialize map for vhost devices. */ dev->tx_q[i].map = OVS_VHOST_QUEUE_MAP_UNKNOWN; rte_spinlock_init(&dev->tx_q[i].tx_lock); @@ -1088,16 +1068,15 @@ netdev_dpdk_rxq_dealloc(struct netdev_rxq *rxq) } static inline void -dpdk_queue_flush__(struct netdev_dpdk *dev, int qid) +netdev_dpdk_eth_tx_burst(struct netdev_dpdk *dev, int qid, + struct rte_mbuf **pkts, int cnt) { - struct dpdk_tx_queue *txq = &dev->tx_q[qid]; uint32_t nb_tx = 0; - while (nb_tx != txq->count) { + while (nb_tx != cnt) { uint32_t ret; - ret = rte_eth_tx_burst(dev->port_id, qid, txq->burst_pkts + nb_tx, - txq->count - nb_tx); + ret = rte_eth_tx_burst(dev->port_id, qid, pkts + nb_tx, cnt - nb_tx); if (!ret) { break; } @@ -1105,32 +1084,18 @@ dpdk_queue_flush__(struct netdev_dpdk *dev, int qid) nb_tx += ret; } - if (OVS_UNLIKELY(nb_tx != txq->count)) { + if (OVS_UNLIKELY(nb_tx != cnt)) { /* free buffers, which we couldn't transmit, one at a time (each * packet could come from a different mempool) */ int i; - for (i = nb_tx; i < txq->count; i++) { - rte_pktmbuf_free(txq->burst_pkts[i]); + for (i = nb_tx; i < cnt; i++) { + rte_pktmbuf_free(pkts[i]); } rte_spinlock_lock(&dev->stats_lock); - dev->stats.tx_dropped += txq->count-nb_tx; + dev->stats.tx_dropped += cnt - nb_tx; rte_spinlock_unlock(&dev->stats_lock); } - - txq->count = 0; - txq->tsc = rte_get_timer_cycles(); -} - -static inline void -dpdk_queue_flush(struct netdev_dpdk *dev, int qid) -{ - struct dpdk_tx_queue *txq = &dev->tx_q[qid]; - - if (txq->count == 0) { - return; - } - dpdk_queue_flush__(dev, qid); } static inline bool @@ -1303,15 +1268,6 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq, struct dp_packet **packets, int nb_rx; int dropped = 0; - /* There is only one tx queue for this core. Do not flush other - * queues. - * Do not flush tx queue which is shared among CPUs - * since it is always flushed */ - if (rxq->queue_id == rte_lcore_id() && - OVS_LIKELY(!dev->txq_needs_locking)) { - dpdk_queue_flush(dev, rxq->queue_id); - } - nb_rx = rte_eth_rx_burst(rx->port_id, rxq->queue_id, (struct rte_mbuf **) packets, NETDEV_MAX_BURST); @@ -1433,35 +1389,6 @@ out: } } -inline static void -dpdk_queue_pkts(struct netdev_dpdk *dev, int qid, - struct rte_mbuf **pkts, int cnt) -{ - struct dpdk_tx_queue *txq = &dev->tx_q[qid]; - uint64_t diff_tsc; - - int i = 0; - - while (i < cnt) { - int freeslots = MAX_TX_QUEUE_LEN - txq->count; - int tocopy = MIN(freeslots, cnt-i); - - memcpy(&txq->burst_pkts[txq->count], &pkts[i], - tocopy * sizeof (struct rte_mbuf *)); - - txq->count += tocopy; - i += tocopy; - - if (txq->count == MAX_TX_QUEUE_LEN || txq->flush_tx) { - dpdk_queue_flush__(dev, qid); - } - diff_tsc = rte_get_timer_cycles() - txq->tsc; - if (diff_tsc >= DRAIN_TSC) { - dpdk_queue_flush__(dev, qid); - } - } -} - /* Tx function. Transmit packets indefinitely */ static void dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet **pkts, @@ -1527,8 +1454,7 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet **pkts, newcnt = netdev_dpdk_qos_run__(dev, mbufs, newcnt); dropped += qos_pkts - newcnt; - dpdk_queue_pkts(dev, qid, mbufs, newcnt); - dpdk_queue_flush(dev, qid); + netdev_dpdk_eth_tx_burst(dev, qid, mbufs, newcnt); } if (OVS_UNLIKELY(dropped)) { @@ -1611,7 +1537,7 @@ netdev_dpdk_send__(struct netdev_dpdk *dev, int qid, temp_cnt = netdev_dpdk_qos_run__(dev, (struct rte_mbuf**)pkts, temp_cnt); dropped += qos_pkts - temp_cnt; - dpdk_queue_pkts(dev, qid, + netdev_dpdk_eth_tx_burst(dev, qid, (struct rte_mbuf **)&pkts[next_tx_idx], temp_cnt); @@ -1631,8 +1557,9 @@ netdev_dpdk_send__(struct netdev_dpdk *dev, int qid, cnt = netdev_dpdk_qos_run__(dev, (struct rte_mbuf**)pkts, cnt); dropped += qos_pkts - cnt; - dpdk_queue_pkts(dev, qid, (struct rte_mbuf **)&pkts[next_tx_idx], - cnt); + netdev_dpdk_eth_tx_burst(dev, qid, + (struct rte_mbuf **)&pkts[next_tx_idx], + cnt); } if (OVS_UNLIKELY(dropped)) {