[dpdk-dev] [PATCH v3 3/3] net/af_xdp: preferred busy polling
Ciara Loftus
ciara.loftus at intel.com
Wed Mar 10 08:48:16 CET 2021
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.loftus at intel.com>
---
doc/guides/nics/af_xdp.rst | 38 ++++++-
doc/guides/rel_notes/release_21_05.rst | 4 +
drivers/net/af_xdp/compat.h | 14 +++
drivers/net/af_xdp/rte_eth_af_xdp.c | 135 +++++++++++++++++++++++--
4 files changed, 179 insertions(+), 12 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/doc/guides/rel_notes/release_21_05.rst b/doc/guides/rel_notes/release_21_05.rst
index 23f7f0bff9..368e41fcb3 100644
--- a/doc/guides/rel_notes/release_21_05.rst
+++ b/doc/guides/rel_notes/release_21_05.rst
@@ -65,6 +65,10 @@ New Features
* Added support for txgbevf PMD.
+* **Updated the AF_XDP driver.**
+
+ * Added support for preferred busy polling.
+
* **Updated testpmd.**
* Added command to display Rx queue used descriptor count.
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 @@ 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;
@@ -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=<int> "
"queue_count=<int> "
"shared_umem=<int> "
- "xdp_prog=<string> ");
+ "xdp_prog=<string> "
+ "busy_budget=<int>");
--
2.17.1
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