[ovs-dev] [PATCHv6] netdev-afxdp: Add need_wakeup supprt.
William Tu
u9012063 at gmail.com
Wed Oct 23 21:06:01 UTC 2019
The patch adds support for using need_wakeup flag in AF_XDP rings.
A new option, use_need_wakeup, is added. When this option is used,
it means that OVS has to explicitly wake up the kernel RX, using poll()
syscall and wake up TX, using sendto() syscall. This feature improves
the performance by avoiding unnecessary sendto syscalls for TX.
For RX, instead of kernel always busy-spinning on fille queue, OVS wakes
up the kernel RX processing when fill queue is replenished.
The need_wakeup feature is merged into Linux kernel bpf-next tee with commit
77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP rings") and
OVS enables it by default, if libbpf supports it. If users enable it but
runs in an older version of libbpf, then the need_wakeup feature has no effect,
and a warning message is logged.
For virtual interface, it's better set use_need_wakeup=false, since
the virtual device's AF_XDP xmit is synchronous: the sendto syscall
enters kernel and process the TX packet on tx queue directly.
On Intel Xeon E5-2620 v3 2.4GHz system, performance of physical port
to physical port improves from 6.1Mpps to 7.3Mpps.
Suggested-by: Ilya Maximets <i.maximets at ovn.org>
Signed-off-by: William Tu <u9012063 at gmail.com>
---
v6:
- address feedback from Ilay
- change default to true only when libbpf supports it.
- update afxdp docs and commit message.
- Tested-at: https://travis-ci.org/williamtu/ovs-travis/builds/601995462
- P2P Performance using 1 pmd, without IRQ pinning
ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=0x40
- Without need_wakeup, 6Mpps
root at ovs-smartnic:~/ovs# ovs-appctl dpif-netdev/pmd-stats-show
pmd thread numa_id 0 core_id 6:
packets received: 68726373
packet recirculations: 0
avg. datapath passes per packet: 1.00
emc hits: 68726213
smc hits: 0
megaflow hits: 159
avg. subtable lookups per megaflow hit: 1.00
miss with success upcall: 1
miss with failed upcall: 0
avg. packets per output batch: 31.84
idle cycles: 10949448171 (29.21%)
processing cycles: 26533605726 (70.79%)
avg cycles per packet: 545.40 (37483053897/68726373)
avg processing cycles per packet: 386.08 (26533605726/68726373)
- With need_wakeup, 7.3Mpps
root at ovs-smartnic:~/ovs# ovs-appctl dpif-netdev/pmd-stats-show
pmd thread numa_id 0 core_id 6:
packets received: 87960016
packet recirculations: 0
avg. datapath passes per packet: 1.00
emc hits: 87959920
smc hits: 0
megaflow hits: 63
avg. subtable lookups per megaflow hit: 1.00
miss with success upcall: 1
miss with failed upcall: 0
avg. packets per output batch: 31.94
idle cycles: 11821505245 (30.87%)
processing cycles: 26468478120 (69.13%)
avg cycles per packet: 435.31 (38289983365/87960016)
avg processing cycles per packet: 300.91 (26468478120/87960016)
v5:
- address feedback from Ilya
- update commit msg about kernel version using bpf-next tree
- remove __func__, and use DBG in log_
- fix alignment
- remove the kernel version requirement for need_wakeup, we can
wait until tag is available
v4:
- move use_need_wakeup check inside xsk_rx_wakeup_if_needed
v3:
- add warning when user enables it but libbpf not support it
- revise documentation
v2:
- address feedbacks from Ilya and Eelco
- add options:use_need_wakeup, default to true
- remove poll timeout=1sec, make poll() return immediately
- naming change: rename to xsk_rx_wakeup_if_needing
- fix indents and return value for errno
---
Documentation/intro/install/afxdp.rst | 14 ++++-
acinclude.m4 | 5 ++
lib/netdev-afxdp.c | 115 ++++++++++++++++++++++++++++++----
lib/netdev-linux-private.h | 2 +
vswitchd/vswitch.xml | 12 ++++
5 files changed, 132 insertions(+), 16 deletions(-)
diff --git a/Documentation/intro/install/afxdp.rst b/Documentation/intro/install/afxdp.rst
index 820e9d993d8f..af8f5ca1826b 100644
--- a/Documentation/intro/install/afxdp.rst
+++ b/Documentation/intro/install/afxdp.rst
@@ -176,9 +176,17 @@ in :doc:`general`::
ovs-vswitchd ...
ovs-vsctl -- add-br br0 -- set Bridge br0 datapath_type=netdev
-Make sure your device driver support AF_XDP, and to use 1 PMD (on core 4)
-on 1 queue (queue 0) device, configure these options: **pmd-cpu-mask,
-pmd-rxq-affinity, and n_rxq**. The **xdpmode** can be "drv" or "skb"::
+Make sure your device driver support AF_XDP, netdev-afxdp supports
+the following additional options (see man ovs-vswitchd.conf.db for
+more details):
+
+ * **xdpmode**: use "drv" for driver mode, or "skb" for skb mode.
+
+ * **use_need_wakeup**: default "true" if libbpf supports it, otherwise false.
+
+For example, to use 1 PMD (on core 4) on 1 queue (queue 0) device,
+configure these options: **pmd-cpu-mask, pmd-rxq-affinity, and n_rxq**.
+The **xdpmode** can be "drv" or "skb"::
ethtool -L enp2s0 combined 1
ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=0x10
diff --git a/acinclude.m4 b/acinclude.m4
index 07c83b15bcbc..370cc43850be 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -276,6 +276,11 @@ AC_DEFUN([OVS_CHECK_LINUX_AF_XDP], [
[Define to 1 if AF_XDP support is available and enabled.])
LIBBPF_LDADD=" -lbpf -lelf"
AC_SUBST([LIBBPF_LDADD])
+
+ AC_CHECK_DECL([xsk_ring_prod__needs_wakeup], [
+ AC_DEFINE([HAVE_XDP_NEED_WAKEUP], [1],
+ [XDP need wakeup support detected in xsk.h.])
+ ], [], [[#include <bpf/xsk.h>]])
fi
AM_CONDITIONAL([HAVE_AF_XDP], test "$AF_XDP_ENABLE" = true)
])
diff --git a/lib/netdev-afxdp.c b/lib/netdev-afxdp.c
index 8eb270c150e8..60259bdd3c86 100644
--- a/lib/netdev-afxdp.c
+++ b/lib/netdev-afxdp.c
@@ -26,6 +26,7 @@
#include <linux/rtnetlink.h>
#include <linux/if_xdp.h>
#include <net/if.h>
+#include <poll.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/socket.h>
@@ -67,6 +68,12 @@ static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
#define PROD_NUM_DESCS XSK_RING_PROD__DEFAULT_NUM_DESCS
#define CONS_NUM_DESCS XSK_RING_CONS__DEFAULT_NUM_DESCS
+#ifdef HAVE_XDP_NEED_WAKEUP
+#define NEED_WAKEUP_DEFAULT true
+#else
+#define NEED_WAKEUP_DEFAULT false
+#endif
+
/* The worst case is all 4 queues TX/CQ/RX/FILL are full + some packets
* still on processing in threads. Number of packets currently in OVS
* processing is hard to estimate because it depends on number of ports.
@@ -82,7 +89,7 @@ BUILD_ASSERT_DECL(PROD_NUM_DESCS == CONS_NUM_DESCS);
#define UMEM2DESC(elem, base) ((uint64_t)((char *)elem - (char *)base))
static struct xsk_socket_info *xsk_configure(int ifindex, int xdp_queue_id,
- int mode);
+ int mode, bool use_need_wakeup);
static void xsk_remove_xdp_program(uint32_t ifindex, int xdpmode);
static void xsk_destroy(struct xsk_socket_info *xsk);
static int xsk_configure_all(struct netdev *netdev);
@@ -117,6 +124,54 @@ struct xsk_socket_info {
atomic_uint64_t tx_dropped;
};
+#ifdef HAVE_XDP_NEED_WAKEUP
+static inline void
+xsk_rx_wakeup_if_needed(struct xsk_umem_info *umem,
+ struct netdev *netdev, int fd)
+{
+ struct netdev_linux *dev = netdev_linux_cast(netdev);
+ struct pollfd pfd;
+ int ret;
+
+ if (!dev->use_need_wakeup) {
+ return;
+ }
+
+ if (xsk_ring_prod__needs_wakeup(&umem->fq)) {
+ pfd.fd = fd;
+ pfd.events = POLLIN;
+
+ ret = poll(&pfd, 1, 0);
+ if (OVS_UNLIKELY(ret < 0)) {
+ VLOG_WARN_RL(&rl, "%s: error polling rx fd: %s.",
+ netdev_get_name(netdev),
+ ovs_strerror(errno));
+ }
+ }
+}
+
+static inline bool
+xsk_tx_need_wakeup(struct xsk_socket_info *xsk_info)
+{
+ return xsk_ring_prod__needs_wakeup(&xsk_info->tx);
+}
+
+#else /* !HAVE_XDP_NEED_WAKEUP */
+static inline void
+xsk_rx_wakeup_if_needed(struct xsk_umem_info *umem OVS_UNUSED,
+ struct netdev *netdev OVS_UNUSED,
+ int fd OVS_UNUSED)
+{
+ /* Nothing. */
+}
+
+static inline bool
+xsk_tx_need_wakeup(struct xsk_socket_info *xsk_info OVS_UNUSED)
+{
+ return true;
+}
+#endif /* HAVE_XDP_NEED_WAKEUP */
+
static void
netdev_afxdp_cleanup_unused_pool(struct unused_pool *pool)
{
@@ -235,7 +290,7 @@ xsk_configure_umem(void *buffer, uint64_t size, int xdpmode)
static struct xsk_socket_info *
xsk_configure_socket(struct xsk_umem_info *umem, uint32_t ifindex,
- uint32_t queue_id, int xdpmode)
+ uint32_t queue_id, int xdpmode, bool use_need_wakeup)
{
struct xsk_socket_config cfg;
struct xsk_socket_info *xsk;
@@ -258,6 +313,12 @@ xsk_configure_socket(struct xsk_umem_info *umem, uint32_t ifindex,
cfg.xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST | XDP_FLAGS_SKB_MODE;
}
+#ifdef HAVE_XDP_NEED_WAKEUP
+ if (use_need_wakeup) {
+ cfg.bind_flags |= XDP_USE_NEED_WAKEUP;
+ }
+#endif
+
if (if_indextoname(ifindex, devname) == NULL) {
VLOG_ERR("ifindex %d to devname failed (%s)",
ifindex, ovs_strerror(errno));
@@ -268,9 +329,11 @@ xsk_configure_socket(struct xsk_umem_info *umem, uint32_t ifindex,
ret = xsk_socket__create(&xsk->xsk, devname, queue_id, umem->umem,
&xsk->rx, &xsk->tx, &cfg);
if (ret) {
- VLOG_ERR("xsk_socket__create failed (%s) mode: %s qid: %d",
+ VLOG_ERR("xsk_socket__create failed (%s) mode: %s "
+ "use_need_wakeup: %s qid: %d",
ovs_strerror(errno),
xdpmode == XDP_COPY ? "SKB": "DRV",
+ use_need_wakeup ? "true" : "false",
queue_id);
free(xsk);
return NULL;
@@ -312,7 +375,8 @@ xsk_configure_socket(struct xsk_umem_info *umem, uint32_t ifindex,
}
static struct xsk_socket_info *
-xsk_configure(int ifindex, int xdp_queue_id, int xdpmode)
+xsk_configure(int ifindex, int xdp_queue_id, int xdpmode,
+ bool use_need_wakeup)
{
struct xsk_socket_info *xsk;
struct xsk_umem_info *umem;
@@ -335,7 +399,8 @@ xsk_configure(int ifindex, int xdp_queue_id, int xdpmode)
VLOG_DBG("Allocated umem pool at 0x%"PRIxPTR, (uintptr_t) umem);
- xsk = xsk_configure_socket(umem, ifindex, xdp_queue_id, xdpmode);
+ xsk = xsk_configure_socket(umem, ifindex, xdp_queue_id, xdpmode,
+ use_need_wakeup);
if (!xsk) {
/* Clean up umem and xpacket pool. */
if (xsk_umem__delete(umem->umem)) {
@@ -366,9 +431,12 @@ xsk_configure_all(struct netdev *netdev)
/* Configure each queue. */
for (i = 0; i < n_rxq; i++) {
- VLOG_INFO("%s: configure queue %d mode %s", __func__, i,
- dev->xdpmode == XDP_COPY ? "SKB" : "DRV");
- xsk_info = xsk_configure(ifindex, i, dev->xdpmode);
+ VLOG_DBG("%s: configure queue %d mode %s use_need_wakeup %s.",
+ netdev_get_name(netdev), i,
+ dev->xdpmode == XDP_COPY ? "SKB" : "DRV",
+ dev->use_need_wakeup ? "true" : "false");
+ xsk_info = xsk_configure(ifindex, i, dev->xdpmode,
+ dev->use_need_wakeup);
if (!xsk_info) {
VLOG_ERR("Failed to create AF_XDP socket on queue %d.", i);
dev->xsks[i] = NULL;
@@ -460,6 +528,7 @@ netdev_afxdp_set_config(struct netdev *netdev, const struct smap *args,
struct netdev_linux *dev = netdev_linux_cast(netdev);
const char *str_xdpmode;
int xdpmode, new_n_rxq;
+ bool need_wakeup;
ovs_mutex_lock(&dev->mutex);
new_n_rxq = MAX(smap_get_int(args, "n_rxq", NR_QUEUE), 1);
@@ -482,10 +551,20 @@ netdev_afxdp_set_config(struct netdev *netdev, const struct smap *args,
return EINVAL;
}
+ need_wakeup = smap_get_bool(args, "use_need_wakeup", NEED_WAKEUP_DEFAULT);
+#ifndef HAVE_XDP_NEED_WAKEUP
+ if (need_wakeup) {
+ VLOG_WARN("XDP need_wakeup is not supported in libbpf.");
+ need_wakeup = false;
+ }
+#endif
+
if (dev->requested_n_rxq != new_n_rxq
- || dev->requested_xdpmode != xdpmode) {
+ || dev->requested_xdpmode != xdpmode
+ || dev->requested_need_wakeup != need_wakeup) {
dev->requested_n_rxq = new_n_rxq;
dev->requested_xdpmode = xdpmode;
+ dev->requested_need_wakeup = need_wakeup;
netdev_request_reconfigure(netdev);
}
ovs_mutex_unlock(&dev->mutex);
@@ -500,7 +579,9 @@ netdev_afxdp_get_config(const struct netdev *netdev, struct smap *args)
ovs_mutex_lock(&dev->mutex);
smap_add_format(args, "n_rxq", "%d", netdev->n_rxq);
smap_add_format(args, "xdpmode", "%s",
- dev->xdpmode == XDP_ZEROCOPY ? "drv" : "skb");
+ dev->xdpmode == XDP_ZEROCOPY ? "drv" : "skb");
+ smap_add_format(args, "use_need_wakeup", "%s",
+ dev->use_need_wakeup ? "true" : "false");
ovs_mutex_unlock(&dev->mutex);
return 0;
}
@@ -516,6 +597,7 @@ netdev_afxdp_reconfigure(struct netdev *netdev)
if (netdev->n_rxq == dev->requested_n_rxq
&& dev->xdpmode == dev->requested_xdpmode
+ && dev->use_need_wakeup == dev->requested_need_wakeup
&& dev->xsks) {
goto out;
}
@@ -532,6 +614,7 @@ netdev_afxdp_reconfigure(struct netdev *netdev)
if (setrlimit(RLIMIT_MEMLOCK, &r)) {
VLOG_ERR("setrlimit(RLIMIT_MEMLOCK) failed: %s", ovs_strerror(errno));
}
+ dev->use_need_wakeup = dev->requested_need_wakeup;
err = xsk_configure_all(netdev);
if (err) {
@@ -654,6 +737,7 @@ netdev_afxdp_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet_batch *batch,
rcvd = xsk_ring_cons__peek(&xsk_info->rx, BATCH_SIZE, &idx_rx);
if (!rcvd) {
+ xsk_rx_wakeup_if_needed(umem, netdev, rx->fd);
return EAGAIN;
}
@@ -698,11 +782,15 @@ netdev_afxdp_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet_batch *batch,
}
static inline int
-kick_tx(struct xsk_socket_info *xsk_info, int xdpmode)
+kick_tx(struct xsk_socket_info *xsk_info, int xdpmode, bool use_need_wakeup)
{
int ret, retries;
static const int KERNEL_TX_BATCH_SIZE = 16;
+ if (use_need_wakeup && !xsk_tx_need_wakeup(xsk_info)) {
+ return 0;
+ }
+
/* In SKB_MODE packet transmission is synchronous, and the kernel xmits
* only TX_BATCH_SIZE(16) packets for a single sendmsg syscall.
* So, we have to kick the kernel (n_packets / 16) times to be sure that
@@ -874,7 +962,7 @@ __netdev_afxdp_batch_send(struct netdev *netdev, int qid,
&orig);
COVERAGE_INC(afxdp_tx_full);
afxdp_complete_tx(xsk_info);
- kick_tx(xsk_info, dev->xdpmode);
+ kick_tx(xsk_info, dev->xdpmode, dev->use_need_wakeup);
error = ENOMEM;
goto out;
}
@@ -898,7 +986,7 @@ __netdev_afxdp_batch_send(struct netdev *netdev, int qid,
xsk_ring_prod__submit(&xsk_info->tx, dp_packet_batch_size(batch));
xsk_info->outstanding_tx += dp_packet_batch_size(batch);
- ret = kick_tx(xsk_info, dev->xdpmode);
+ ret = kick_tx(xsk_info, dev->xdpmode, dev->use_need_wakeup);
if (OVS_UNLIKELY(ret)) {
VLOG_WARN_RL(&rl, "%s: error sending AF_XDP packet: %s.",
netdev_get_name(netdev), ovs_strerror(ret));
@@ -968,6 +1056,7 @@ netdev_afxdp_construct(struct netdev *netdev)
dev->requested_n_rxq = NR_QUEUE;
dev->requested_xdpmode = XDP_COPY;
+ dev->requested_need_wakeup = NEED_WAKEUP_DEFAULT;
dev->xsks = NULL;
dev->tx_locks = NULL;
diff --git a/lib/netdev-linux-private.h b/lib/netdev-linux-private.h
index a350be151147..c14f2fb81bb0 100644
--- a/lib/netdev-linux-private.h
+++ b/lib/netdev-linux-private.h
@@ -102,6 +102,8 @@ struct netdev_linux {
int requested_n_rxq;
int xdpmode; /* AF_XDP running mode: driver or skb. */
int requested_xdpmode;
+ bool use_need_wakeup;
+ bool requested_need_wakeup;
struct ovs_spin *tx_locks; /* spin lock array for TX queues. */
#endif
};
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index 01304a5ed2c2..decccfe84971 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -3122,6 +3122,18 @@ ovs-vsctl add-port br0 p0 -- set Interface p0 type=patch options:peer=p1 \
</p>
</column>
+ <column name="options" key="use_need_wakeup"
+ type='{"type": "boolean"}'>
+ <p>
+ Specifies whether to use need_wakeup feature in afxdp netdev.
+ If enabled, OVS explicitly wakes up the kernel RX, using poll()
+ syscall and wakes up TX, using sendto() syscall. For physical
+ devices, this feature improves the performance by avoiding
+ unnecessary sendto syscalls.
+ Defaults to true if supported by libbpf.
+ </p>
+ </column>
+
<column name="options" key="vhost-server-path"
type='{"type": "string"}'>
<p>
--
2.7.4
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