From: Ciara Loftus Date: Wed, 10 Mar 2021 07:48:16 +0000 (+0000) Subject: net/af_xdp: prefer busy polling X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=055a393626ed25ccf92e7c685495a87f6fb6ab52;p=dpdk.git net/af_xdp: prefer busy polling This commit introduces support for preferred busy polling to the AF_XDP PMD. This feature aims to improve single-core performance for AF_XDP sockets under heavy load. A new vdev arg is introduced called 'busy_budget' whose default value is 64. busy_budget is the value supplied to the kernel with the SO_BUSY_POLL_BUDGET socket option and represents the busy-polling NAPI budget. To set the budget to a different value eg. 256: --vdev=net_af_xdp0,iface=eth0,busy_budget=256 Preferred busy polling is enabled by default provided a kernel with version >= v5.11 is in use. To disable it, set the budget to zero. The following settings are also strongly recommended to be used in conjunction with this feature: echo 2 | sudo tee /sys/class/net/eth0/napi_defer_hard_irqs echo 200000 | sudo tee /sys/class/net/eth0/gro_flush_timeout .. where eth0 is the interface being used by the PMD. Signed-off-by: Ciara Loftus Reviewed-by: Ferruh Yigit --- diff --git a/doc/guides/nics/af_xdp.rst b/doc/guides/nics/af_xdp.rst index 5ed24374f8..8bf40b5f0f 100644 --- a/doc/guides/nics/af_xdp.rst +++ b/doc/guides/nics/af_xdp.rst @@ -35,6 +35,7 @@ The following options can be provided to set up an af_xdp port in DPDK. * ``shared_umem`` - PMD will attempt to share UMEM with others (optional, default 0); * ``xdp_prog`` - path to custom xdp program (optional, default none); +* ``busy_budget`` - busy polling budget (optional, default 64); Prerequisites ------------- @@ -51,6 +52,7 @@ This is a Linux-specific PMD, thus the following prerequisites apply: * For shared_umem, it requires kernel version v5.10 or later and libbpf version v0.2.0 or later. * For 32-bit OS, a kernel with version 5.4 or later is required. +* For busy polling, kernel version v5.11 or later is required. Set up an af_xdp interface ----------------------------- @@ -107,4 +109,38 @@ Limitations .. code-block:: console --vdev net_af_xdp0,iface=ens786f1,shared_umem=1 \ - --vdev net_af_xdp1,iface=ens786f2,shared_umem=1 \ \ No newline at end of file + --vdev net_af_xdp1,iface=ens786f2,shared_umem=1 \ + +- **Preferred Busy Polling** + + The SO_PREFER_BUSY_POLL socket option was introduced in kernel v5.11. It can + deliver a performance improvement for sockets with heavy traffic loads and + can significantly improve single-core performance in this context. + + The feature is enabled by default in the AF_XDP PMD. To disable it, set the + 'busy_budget' vdevarg to zero: + + .. code-block:: console + + --vdev net_af_xdp0,iface=ens786f1,busy_budget=0 + + The default 'busy_budget' is 64 and it represents the number of packets the + kernel will attempt to process in the netdev's NAPI context. You can change + the value for example to 256 like so: + + .. code-block:: console + + --vdev net_af_xdp0,iface=ens786f1,busy_budget=256 + + It is also strongly recommended to set the following for optimal performance: + + .. code-block:: console + + echo 2 | sudo tee /sys/class/net/ens786f1/napi_defer_hard_irqs + echo 200000 | sudo tee /sys/class/net/ens786f1/gro_flush_timeout + + The above defers interrupts for interface ens786f1 and instead schedules its + NAPI context from a watchdog timer instead of from softirqs. More information + on this feature can be found at [1]. + + [1] https://lwn.net/Articles/837010/ \ No newline at end of file diff --git a/doc/guides/rel_notes/release_21_05.rst b/doc/guides/rel_notes/release_21_05.rst index 21dc6d2342..32f012762b 100644 --- a/doc/guides/rel_notes/release_21_05.rst +++ b/doc/guides/rel_notes/release_21_05.rst @@ -76,6 +76,10 @@ New Features * Added support for txgbevf PMD. +* **Updated the AF_XDP driver.** + + * Added support for preferred busy polling. + * **Updated testpmd.** * Added a command line option to configure forced speed for Ethernet port. diff --git a/drivers/net/af_xdp/compat.h b/drivers/net/af_xdp/compat.h index 7aa40d522e..545c8aa395 100644 --- a/drivers/net/af_xdp/compat.h +++ b/drivers/net/af_xdp/compat.h @@ -39,3 +39,17 @@ create_shared_socket(struct xsk_socket **xsk_ptr __rte_unused, return -1; } #endif + +#ifdef XDP_USE_NEED_WAKEUP +static int +syscall_needed(struct xsk_ring_prod *q, uint32_t busy_budget) +{ + return xsk_ring_prod__needs_wakeup(q) | busy_budget; +} +#else +static int +syscall_needed(struct xsk_ring_prod *q __rte_unused, uint32_t busy_budget) +{ + return busy_budget; +} +#endif diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c index 9c0e935cd3..a64fef1cf5 100644 --- a/drivers/net/af_xdp/rte_eth_af_xdp.c +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c @@ -41,6 +41,13 @@ #include "compat.h" +#ifndef SO_PREFER_BUSY_POLL +#define SO_PREFER_BUSY_POLL 69 +#endif +#ifndef SO_BUSY_POLL_BUDGET +#define SO_BUSY_POLL_BUDGET 70 +#endif + #ifndef SOL_XDP #define SOL_XDP 283 @@ -65,6 +72,8 @@ RTE_LOG_REGISTER(af_xdp_logtype, pmd.net.af_xdp, NOTICE); #define ETH_AF_XDP_DFLT_NUM_DESCS XSK_RING_CONS__DEFAULT_NUM_DESCS #define ETH_AF_XDP_DFLT_START_QUEUE_IDX 0 #define ETH_AF_XDP_DFLT_QUEUE_COUNT 1 +#define ETH_AF_XDP_DFLT_BUSY_BUDGET 64 +#define ETH_AF_XDP_DFLT_BUSY_TIMEOUT 20 #define ETH_AF_XDP_RX_BATCH_SIZE XSK_RING_CONS__DEFAULT_NUM_DESCS #define ETH_AF_XDP_TX_BATCH_SIZE XSK_RING_CONS__DEFAULT_NUM_DESCS @@ -100,6 +109,7 @@ struct pkt_rx_queue { struct pkt_tx_queue *pair; struct pollfd fds[1]; int xsk_queue_idx; + int busy_budget; }; struct tx_stats { @@ -140,6 +150,7 @@ struct pmd_internals { #define ETH_AF_XDP_QUEUE_COUNT_ARG "queue_count" #define ETH_AF_XDP_SHARED_UMEM_ARG "shared_umem" #define ETH_AF_XDP_PROG_ARG "xdp_prog" +#define ETH_AF_XDP_BUDGET_ARG "busy_budget" static const char * const valid_arguments[] = { ETH_AF_XDP_IFACE_ARG, @@ -147,6 +158,7 @@ static const char * const valid_arguments[] = { ETH_AF_XDP_QUEUE_COUNT_ARG, ETH_AF_XDP_SHARED_UMEM_ARG, ETH_AF_XDP_PROG_ARG, + ETH_AF_XDP_BUDGET_ARG, NULL }; @@ -261,11 +273,9 @@ af_xdp_rx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) nb_pkts = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx); if (nb_pkts == 0) { -#if defined(XDP_USE_NEED_WAKEUP) - if (xsk_ring_prod__needs_wakeup(fq)) + if (syscall_needed(&rxq->fq, rxq->busy_budget)) recvfrom(xsk_socket__fd(rxq->xsk), NULL, 0, MSG_DONTWAIT, NULL, NULL); -#endif return 0; } @@ -446,9 +456,7 @@ kick_tx(struct pkt_tx_queue *txq, struct xsk_ring_cons *cq) pull_umem_cq(umem, XSK_RING_CONS__DEFAULT_NUM_DESCS, cq); -#if defined(XDP_USE_NEED_WAKEUP) - if (xsk_ring_prod__needs_wakeup(&txq->tx)) -#endif + if (syscall_needed(&txq->tx, txq->pair->busy_budget)) while (send(xsk_socket__fd(txq->pair->xsk), NULL, 0, MSG_DONTWAIT) < 0) { /* some thing unexpected */ @@ -795,6 +803,8 @@ eth_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info) dev_info->max_mtu = ETH_AF_XDP_FRAME_SIZE - XDP_PACKET_HEADROOM; #endif + dev_info->default_rxportconf.burst_size = ETH_AF_XDP_DFLT_BUSY_BUDGET; + dev_info->default_txportconf.burst_size = ETH_AF_XDP_DFLT_BUSY_BUDGET; dev_info->default_rxportconf.nb_queues = 1; dev_info->default_txportconf.nb_queues = 1; dev_info->default_rxportconf.ring_size = ETH_AF_XDP_DFLT_NUM_DESCS; @@ -1142,6 +1152,65 @@ load_custom_xdp_prog(const char *prog_path, int if_index) return 0; } +/* Detect support for busy polling through setsockopt(). */ +static int +configure_preferred_busy_poll(struct pkt_rx_queue *rxq) +{ + int sock_opt = 1; + int fd = xsk_socket__fd(rxq->xsk); + int ret = 0; + + ret = setsockopt(fd, SOL_SOCKET, SO_PREFER_BUSY_POLL, + (void *)&sock_opt, sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(DEBUG, "Failed to set SO_PREFER_BUSY_POLL\n"); + goto err_prefer; + } + + sock_opt = ETH_AF_XDP_DFLT_BUSY_TIMEOUT; + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL, (void *)&sock_opt, + sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(DEBUG, "Failed to set SO_BUSY_POLL\n"); + goto err_timeout; + } + + sock_opt = rxq->busy_budget; + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL_BUDGET, + (void *)&sock_opt, sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(DEBUG, "Failed to set SO_BUSY_POLL_BUDGET\n"); + } else { + AF_XDP_LOG(INFO, "Busy polling budget set to: %u\n", + rxq->busy_budget); + return 0; + } + + /* setsockopt failure - attempt to restore xsk to default state and + * proceed without busy polling support. + */ + sock_opt = 0; + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL, (void *)&sock_opt, + sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(ERR, "Failed to unset SO_BUSY_POLL\n"); + return -1; + } + +err_timeout: + sock_opt = 0; + ret = setsockopt(fd, SOL_SOCKET, SO_PREFER_BUSY_POLL, + (void *)&sock_opt, sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(ERR, "Failed to unset SO_PREFER_BUSY_POLL\n"); + return -1; + } + +err_prefer: + rxq->busy_budget = 0; + return 0; +} + static int xsk_configure(struct pmd_internals *internals, struct pkt_rx_queue *rxq, int ring_size) @@ -1200,6 +1269,15 @@ xsk_configure(struct pmd_internals *internals, struct pkt_rx_queue *rxq, goto err; } #endif + + if (rxq->busy_budget) { + ret = configure_preferred_busy_poll(rxq); + if (ret) { + AF_XDP_LOG(ERR, "Failed configure busy polling.\n"); + goto err; + } + } + ret = reserve_fill_queue(rxq->umem, reserve_size, fq_bufs, &rxq->fq); if (ret) { xsk_socket__delete(rxq->xsk); @@ -1257,6 +1335,9 @@ eth_rx_queue_setup(struct rte_eth_dev *dev, goto err; } + if (!rxq->busy_budget) + AF_XDP_LOG(DEBUG, "Preferred busy polling not enabled\n"); + rxq->fds[0].fd = xsk_socket__fd(rxq->xsk); rxq->fds[0].events = POLLIN; @@ -1363,6 +1444,24 @@ static const struct eth_dev_ops ops = { .stats_reset = eth_stats_reset, }; +/** parse busy_budget argument */ +static int +parse_budget_arg(const char *key __rte_unused, + const char *value, void *extra_args) +{ + int *i = (int *)extra_args; + char *end; + + *i = strtol(value, &end, 10); + if (*i < 0 || *i > UINT16_MAX) { + AF_XDP_LOG(ERR, "Invalid busy_budget %i, must be >= 0 and <= %u\n", + *i, UINT16_MAX); + return -EINVAL; + } + + return 0; +} + /** parse integer from integer argument */ static int parse_integer_arg(const char *key __rte_unused, @@ -1465,7 +1564,8 @@ xdp_get_channels_info(const char *if_name, int *max_queues, static int parse_parameters(struct rte_kvargs *kvlist, char *if_name, int *start_queue, - int *queue_cnt, int *shared_umem, char *prog_path) + int *queue_cnt, int *shared_umem, char *prog_path, + int *busy_budget) { int ret; @@ -1496,6 +1596,11 @@ parse_parameters(struct rte_kvargs *kvlist, char *if_name, int *start_queue, if (ret < 0) goto free_kvlist; + ret = rte_kvargs_process(kvlist, ETH_AF_XDP_BUDGET_ARG, + &parse_budget_arg, busy_budget); + if (ret < 0) + goto free_kvlist; + free_kvlist: rte_kvargs_free(kvlist); return ret; @@ -1534,7 +1639,7 @@ error: static struct rte_eth_dev * init_internals(struct rte_vdev_device *dev, const char *if_name, int start_queue_idx, int queue_cnt, int shared_umem, - const char *prog_path) + const char *prog_path, int busy_budget) { const char *name = rte_vdev_device_name(dev); const unsigned int numa_node = dev->device.numa_node; @@ -1595,6 +1700,7 @@ init_internals(struct rte_vdev_device *dev, const char *if_name, internals->rx_queues[i].pair = &internals->tx_queues[i]; internals->rx_queues[i].xsk_queue_idx = start_queue_idx + i; internals->tx_queues[i].xsk_queue_idx = start_queue_idx + i; + internals->rx_queues[i].busy_budget = busy_budget; } ret = get_iface_info(if_name, &internals->eth_addr, @@ -1638,6 +1744,7 @@ rte_pmd_af_xdp_probe(struct rte_vdev_device *dev) int xsk_queue_cnt = ETH_AF_XDP_DFLT_QUEUE_COUNT; int shared_umem = 0; char prog_path[PATH_MAX] = {'\0'}; + int busy_budget = -1; struct rte_eth_dev *eth_dev = NULL; const char *name; @@ -1667,7 +1774,8 @@ rte_pmd_af_xdp_probe(struct rte_vdev_device *dev) dev->device.numa_node = rte_socket_id(); if (parse_parameters(kvlist, if_name, &xsk_start_queue_idx, - &xsk_queue_cnt, &shared_umem, prog_path) < 0) { + &xsk_queue_cnt, &shared_umem, prog_path, + &busy_budget) < 0) { AF_XDP_LOG(ERR, "Invalid kvargs value\n"); return -EINVAL; } @@ -1677,8 +1785,12 @@ rte_pmd_af_xdp_probe(struct rte_vdev_device *dev) return -EINVAL; } + busy_budget = busy_budget == -1 ? ETH_AF_XDP_DFLT_BUSY_BUDGET : + busy_budget; + eth_dev = init_internals(dev, if_name, xsk_start_queue_idx, - xsk_queue_cnt, shared_umem, prog_path); + xsk_queue_cnt, shared_umem, prog_path, + busy_budget); if (eth_dev == NULL) { AF_XDP_LOG(ERR, "Failed to init internals\n"); return -1; @@ -1723,4 +1835,5 @@ RTE_PMD_REGISTER_PARAM_STRING(net_af_xdp, "start_queue= " "queue_count= " "shared_umem= " - "xdp_prog= "); + "xdp_prog= " + "busy_budget=");