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 <ciara.lof...@intel.com> --- doc/guides/nics/af_xdp.rst | 38 ++++++++++++- drivers/net/af_xdp/compat.h | 13 +++++ drivers/net/af_xdp/rte_eth_af_xdp.c | 85 ++++++++++++++++++++++++----- 3 files changed, 121 insertions(+), 15 deletions(-) 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/drivers/net/af_xdp/compat.h b/drivers/net/af_xdp/compat.h index 7aa40d522e..1d247a50b2 100644 --- a/drivers/net/af_xdp/compat.h +++ b/drivers/net/af_xdp/compat.h @@ -39,3 +39,16 @@ 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 +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 34b15aa3d0..5091239b38 100644 --- a/drivers/net/af_xdp/rte_eth_af_xdp.c +++ b/drivers/net/af_xdp/rte_eth_af_xdp.c @@ -65,6 +65,8 @@ 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 512 #define ETH_AF_XDP_TX_BATCH_SIZE 512 @@ -100,6 +102,7 @@ struct pkt_rx_queue { struct pkt_tx_queue *pair; struct pollfd fds[1]; int xsk_queue_idx; + uint32_t busy_budget; }; struct tx_stats { @@ -140,6 +143,7 @@ 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 +151,7 @@ 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 +266,9 @@ 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; } @@ -334,11 +337,9 @@ af_xdp_rx_cp(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; } @@ -422,9 +423,7 @@ 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 */ @@ -437,6 +436,7 @@ kick_tx(struct pkt_tx_queue *txq, struct xsk_ring_cons *cq) XSK_RING_CONS__DEFAULT_NUM_DESCS, cq); } + } } #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG) @@ -1145,6 +1145,39 @@ xsk_configure(struct pmd_internals *internals, struct pkt_rx_queue *rxq, goto err; } +#ifdef SO_PREFER_BUSY_POLL + if (rxq->busy_budget) { + int sock_opt = 1; + int fd = xsk_socket__fd(rxq->xsk); + + ret = setsockopt(fd, SOL_SOCKET, SO_PREFER_BUSY_POLL, + (void *)&sock_opt, sizeof(sock_opt)); + if (ret < 0) { + AF_XDP_LOG(ERR, "Failed to set SO_PREFER_BUSY_POLL\n"); + goto err; + } + + 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(ERR, "Failed to set SO_BUSY_POLL\n"); + goto err; + } + + 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(ERR, "Failed to set SO_BUSY_POLL_BUDGET\n"); + goto err; + } else { + AF_XDP_LOG(INFO, "Busy polling budget set to: %u\n", + rxq->busy_budget); + } + } +#endif + #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG) if (rte_pktmbuf_alloc_bulk(rxq->umem->mb_pool, fq_bufs, reserve_size)) { AF_XDP_LOG(DEBUG, "Failed to get enough buffers for fq.\n"); @@ -1416,7 +1449,8 @@ 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; @@ -1447,6 +1481,11 @@ 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_integer_arg, busy_budget); + if (ret < 0) + goto free_kvlist; + free_kvlist: rte_kvargs_free(kvlist); return ret; @@ -1485,7 +1524,7 @@ get_iface_info(const char *if_name, 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; @@ -1546,6 +1585,7 @@ 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, @@ -1589,6 +1629,7 @@ 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; @@ -1618,7 +1659,8 @@ 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; } @@ -1628,8 +1670,22 @@ rte_pmd_af_xdp_probe(struct rte_vdev_device *dev) return -EINVAL; } +#ifdef SO_PREFER_BUSY_POLL + busy_budget = busy_budget == -1 ? ETH_AF_XDP_DFLT_BUSY_BUDGET : + busy_budget; + if (!busy_budget) + AF_XDP_LOG(ERR, "Preferred busy polling disabled\n"); +#else + if (busy_budget > 0) { + AF_XDP_LOG(ERR, "Kernel does not support SO_PREFER_BUSY_POLL\n"); + return -ENOTSUP; + } + busy_budget = 0; +#endif + 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; @@ -1674,4 +1730,5 @@ RTE_PMD_REGISTER_PARAM_STRING(net_af_xdp, "start_queue=<int> " "queue_count=<int> " "shared_umem=<int> " - "xdp_prog=<string> "); + "xdp_prog=<string> " + "busy_budget=<int>"); -- 2.17.1