[openwrt/openwrt] kernel: add patch that adds support for running threaded NAPI poll functions
LEDE Commits
lede-commits at lists.infradead.org
Sat Aug 22 01:02:27 EDT 2020
nbd pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/f51f18e0998568e6a53c834b50f8fa1b20f634f3
commit f51f18e0998568e6a53c834b50f8fa1b20f634f3
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Sun Jul 26 15:24:42 2020 +0200
kernel: add patch that adds support for running threaded NAPI poll functions
This is helps on workloads with CPU intensive poll functions (e.g. 802.11)
on multicore systems
Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
.../linux/generic/hack-4.14/721-phy_packets.patch | 10 +-
.../linux/generic/hack-4.19/721-phy_packets.patch | 10 +-
.../linux/generic/hack-5.4/721-phy_packets.patch | 10 +-
...net-add-support-for-threaded-NAPI-polling.patch | 339 ++++++++++++++++++++
...net-add-support-for-threaded-NAPI-polling.patch | 339 ++++++++++++++++++++
...net-add-support-for-threaded-NAPI-polling.patch | 343 +++++++++++++++++++++
6 files changed, 1036 insertions(+), 15 deletions(-)
diff --git a/target/linux/generic/hack-4.14/721-phy_packets.patch b/target/linux/generic/hack-4.14/721-phy_packets.patch
index e6e06554de..d67171054d 100644
--- a/target/linux/generic/hack-4.14/721-phy_packets.patch
+++ b/target/linux/generic/hack-4.14/721-phy_packets.patch
@@ -15,7 +15,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
-@@ -1412,6 +1412,7 @@ enum netdev_priv_flags {
+@@ -1415,6 +1415,7 @@ enum netdev_priv_flags {
IFF_PHONY_HEADROOM = 1<<26,
IFF_MACSEC = 1<<27,
IFF_L3MDEV_RX_HANDLER = 1<<28,
@@ -23,7 +23,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
};
#define IFF_802_1Q_VLAN IFF_802_1Q_VLAN
-@@ -1442,6 +1443,7 @@ enum netdev_priv_flags {
+@@ -1445,6 +1446,7 @@ enum netdev_priv_flags {
#define IFF_RXFH_CONFIGURED IFF_RXFH_CONFIGURED
#define IFF_MACSEC IFF_MACSEC
#define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER
@@ -31,7 +31,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
/**
* struct net_device - The DEVICE structure.
-@@ -1728,6 +1730,11 @@ struct net_device {
+@@ -1731,6 +1733,11 @@ struct net_device {
const struct xfrmdev_ops *xfrmdev_ops;
#endif
@@ -43,7 +43,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
const struct header_ops *header_ops;
unsigned int flags;
-@@ -1802,6 +1809,10 @@ struct net_device {
+@@ -1805,6 +1812,10 @@ struct net_device {
struct mpls_dev __rcu *mpls_ptr;
#endif
@@ -101,7 +101,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
help
--- a/net/core/dev.c
+++ b/net/core/dev.c
-@@ -3000,10 +3000,20 @@ static int xmit_one(struct sk_buff *skb,
+@@ -3001,10 +3001,20 @@ static int xmit_one(struct sk_buff *skb,
if (!list_empty(&ptype_all) || !list_empty(&dev->ptype_all))
dev_queue_xmit_nit(skb, dev);
diff --git a/target/linux/generic/hack-4.19/721-phy_packets.patch b/target/linux/generic/hack-4.19/721-phy_packets.patch
index 2bb01718ad..9463ed22c3 100644
--- a/target/linux/generic/hack-4.19/721-phy_packets.patch
+++ b/target/linux/generic/hack-4.19/721-phy_packets.patch
@@ -15,7 +15,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
-@@ -1514,6 +1514,7 @@ enum netdev_priv_flags {
+@@ -1517,6 +1517,7 @@ enum netdev_priv_flags {
IFF_FAILOVER_SLAVE = 1<<28,
IFF_L3MDEV_RX_HANDLER = 1<<29,
IFF_LIVE_RENAME_OK = 1<<30,
@@ -23,7 +23,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
};
#define IFF_802_1Q_VLAN IFF_802_1Q_VLAN
-@@ -1546,6 +1547,7 @@ enum netdev_priv_flags {
+@@ -1549,6 +1550,7 @@ enum netdev_priv_flags {
#define IFF_FAILOVER_SLAVE IFF_FAILOVER_SLAVE
#define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER
#define IFF_LIVE_RENAME_OK IFF_LIVE_RENAME_OK
@@ -31,7 +31,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
/**
* struct net_device - The DEVICE structure.
-@@ -1846,6 +1848,11 @@ struct net_device {
+@@ -1849,6 +1851,11 @@ struct net_device {
const struct tlsdev_ops *tlsdev_ops;
#endif
@@ -43,7 +43,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
const struct header_ops *header_ops;
unsigned int flags;
-@@ -1928,6 +1935,10 @@ struct net_device {
+@@ -1931,6 +1938,10 @@ struct net_device {
struct mpls_dev __rcu *mpls_ptr;
#endif
@@ -101,7 +101,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
help
--- a/net/core/dev.c
+++ b/net/core/dev.c
-@@ -3251,10 +3251,20 @@ static int xmit_one(struct sk_buff *skb,
+@@ -3252,10 +3252,20 @@ static int xmit_one(struct sk_buff *skb,
if (!list_empty(&ptype_all) || !list_empty(&dev->ptype_all))
dev_queue_xmit_nit(skb, dev);
diff --git a/target/linux/generic/hack-5.4/721-phy_packets.patch b/target/linux/generic/hack-5.4/721-phy_packets.patch
index b3008cbbcf..ed18da9e0c 100644
--- a/target/linux/generic/hack-5.4/721-phy_packets.patch
+++ b/target/linux/generic/hack-5.4/721-phy_packets.patch
@@ -15,7 +15,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
-@@ -1546,6 +1546,7 @@ enum netdev_priv_flags {
+@@ -1549,6 +1549,7 @@ enum netdev_priv_flags {
IFF_FAILOVER_SLAVE = 1<<28,
IFF_L3MDEV_RX_HANDLER = 1<<29,
IFF_LIVE_RENAME_OK = 1<<30,
@@ -23,7 +23,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
};
#define IFF_802_1Q_VLAN IFF_802_1Q_VLAN
-@@ -1578,6 +1579,7 @@ enum netdev_priv_flags {
+@@ -1581,6 +1582,7 @@ enum netdev_priv_flags {
#define IFF_FAILOVER_SLAVE IFF_FAILOVER_SLAVE
#define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER
#define IFF_LIVE_RENAME_OK IFF_LIVE_RENAME_OK
@@ -31,7 +31,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
/**
* struct net_device - The DEVICE structure.
-@@ -1879,6 +1881,11 @@ struct net_device {
+@@ -1882,6 +1884,11 @@ struct net_device {
const struct tlsdev_ops *tlsdev_ops;
#endif
@@ -43,7 +43,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
const struct header_ops *header_ops;
unsigned int flags;
-@@ -1961,6 +1968,10 @@ struct net_device {
+@@ -1964,6 +1971,10 @@ struct net_device {
struct mpls_dev __rcu *mpls_ptr;
#endif
@@ -101,7 +101,7 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
help
--- a/net/core/dev.c
+++ b/net/core/dev.c
-@@ -3191,10 +3191,20 @@ static int xmit_one(struct sk_buff *skb,
+@@ -3192,10 +3192,20 @@ static int xmit_one(struct sk_buff *skb,
if (dev_nit_active(dev))
dev_queue_xmit_nit(skb, dev);
diff --git a/target/linux/generic/pending-4.14/690-net-add-support-for-threaded-NAPI-polling.patch b/target/linux/generic/pending-4.14/690-net-add-support-for-threaded-NAPI-polling.patch
new file mode 100644
index 0000000000..1a531cb8fc
--- /dev/null
+++ b/target/linux/generic/pending-4.14/690-net-add-support-for-threaded-NAPI-polling.patch
@@ -0,0 +1,339 @@
+From: Felix Fietkau <nbd at nbd.name>
+Date: Sun, 26 Jul 2020 14:03:21 +0200
+Subject: [PATCH] net: add support for threaded NAPI polling
+
+For some drivers (especially 802.11 drivers), doing a lot of work in the NAPI
+poll function does not perform well. Since NAPI poll is bound to the CPU it
+was scheduled from, we can easily end up with a few very busy CPUs spending
+most of their time in softirq/ksoftirqd and some idle ones.
+
+Introduce threaded NAPI for such drivers based on a workqueue. The API is the
+same except for using netif_threaded_napi_add instead of netif_napi_add.
+
+In my tests with mt76 on MT7621 using threaded NAPI + a thread for tx scheduling
+improves LAN->WLAN bridging throughput by 10-50%. Throughput without threaded
+NAPI is wildly inconsistent, depending on the CPU that runs the tx scheduling
+thread.
+
+With threaded NAPI it seems stable and consistent (and higher than the best
+results I got without it).
+
+Based on a patch by Hillf Danton
+
+Cc: Hillf Danton <hdanton at sina.com>
+Signed-off-by: Felix Fietkau <nbd at nbd.name>
+---
+
+--- a/include/linux/netdevice.h
++++ b/include/linux/netdevice.h
+@@ -326,6 +326,7 @@ struct napi_struct {
+ struct list_head dev_list;
+ struct hlist_node napi_hash_node;
+ unsigned int napi_id;
++ struct work_struct work;
+ };
+
+ enum {
+@@ -336,6 +337,7 @@ enum {
+ NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */
+ NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */
+ NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */
++ NAPI_STATE_THREADED, /* Use threaded NAPI */
+ };
+
+ enum {
+@@ -346,6 +348,7 @@ enum {
+ NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED),
+ NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL),
+ NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL),
++ NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED),
+ };
+
+ enum gro_result {
+@@ -2093,6 +2096,26 @@ void netif_napi_add(struct net_device *d
+ int (*poll)(struct napi_struct *, int), int weight);
+
+ /**
++ * netif_threaded_napi_add - initialize a NAPI context
++ * @dev: network device
++ * @napi: NAPI context
++ * @poll: polling function
++ * @weight: default weight
++ *
++ * This variant of netif_napi_add() should be used from drivers using NAPI
++ * with CPU intensive poll functions.
++ * This will schedule polling from a high priority workqueue
++ */
++static inline void netif_threaded_napi_add(struct net_device *dev,
++ struct napi_struct *napi,
++ int (*poll)(struct napi_struct *, int),
++ int weight)
++{
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ netif_napi_add(dev, napi, poll, weight);
++}
++
++/**
+ * netif_tx_napi_add - initialize a NAPI context
+ * @dev: network device
+ * @napi: NAPI context
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -160,6 +160,7 @@ static DEFINE_SPINLOCK(offload_lock);
+ struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
+ struct list_head ptype_all __read_mostly; /* Taps */
+ static struct list_head offload_base __read_mostly;
++static struct workqueue_struct *napi_workq __read_mostly;
+
+ static int netif_rx_internal(struct sk_buff *skb);
+ static int call_netdevice_notifiers_info(unsigned long val,
+@@ -5237,6 +5238,11 @@ void __napi_schedule(struct napi_struct
+ {
+ unsigned long flags;
+
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ local_irq_save(flags);
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ local_irq_restore(flags);
+@@ -5284,6 +5290,11 @@ EXPORT_SYMBOL(napi_schedule_prep);
+ */
+ void __napi_schedule_irqoff(struct napi_struct *n)
+ {
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ }
+ EXPORT_SYMBOL(__napi_schedule_irqoff);
+@@ -5521,6 +5532,82 @@ static enum hrtimer_restart napi_watchdo
+ return HRTIMER_NORESTART;
+ }
+
++static int __napi_poll(struct napi_struct *n, bool *repoll)
++{
++ int work, weight;
++
++ weight = n->weight;
++
++ /* This NAPI_STATE_SCHED test is for avoiding a race
++ * with netpoll's poll_napi(). Only the entity which
++ * obtains the lock and sees NAPI_STATE_SCHED set will
++ * actually make the ->poll() call. Therefore we avoid
++ * accidentally calling ->poll() when NAPI is not scheduled.
++ */
++ work = 0;
++ if (test_bit(NAPI_STATE_SCHED, &n->state)) {
++ work = n->poll(n, weight);
++ trace_napi_poll(n, work, weight);
++ }
++
++ WARN_ON_ONCE(work > weight);
++
++ if (likely(work < weight))
++ return work;
++
++ /* Drivers must not modify the NAPI state if they
++ * consume the entire weight. In such cases this code
++ * still "owns" the NAPI instance and therefore can
++ * move the instance around on the list at-will.
++ */
++ if (unlikely(napi_disable_pending(n))) {
++ napi_complete(n);
++ return work;
++ }
++
++ if (n->gro_list) {
++ /* flush too old packets
++ * If HZ < 1000, flush all packets.
++ */
++ napi_gro_flush(n, HZ >= 1000);
++ }
++
++ *repoll = true;
++
++ return work;
++}
++
++static void napi_workfn(struct work_struct *work)
++{
++ struct napi_struct *n = container_of(work, struct napi_struct, work);
++ void *have;
++
++ for (;;) {
++ bool repoll = false;
++
++ local_bh_disable();
++
++ have = netpoll_poll_lock(n);
++ __napi_poll(n, &repoll);
++ netpoll_poll_unlock(have);
++
++ local_bh_enable();
++
++ if (!repoll)
++ return;
++
++ if (!need_resched())
++ continue;
++
++ /*
++ * have to pay for the latency of task switch even if
++ * napi is scheduled
++ */
++ queue_work(napi_workq, work);
++ return;
++ }
++}
++
+ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
+ int (*poll)(struct napi_struct *, int), int weight)
+ {
+@@ -5540,6 +5627,7 @@ void netif_napi_add(struct net_device *d
+ #ifdef CONFIG_NETPOLL
+ napi->poll_owner = -1;
+ #endif
++ INIT_WORK(&napi->work, napi_workfn);
+ set_bit(NAPI_STATE_SCHED, &napi->state);
+ napi_hash_add(napi);
+ }
+@@ -5565,6 +5653,7 @@ EXPORT_SYMBOL(napi_disable);
+ void netif_napi_del(struct napi_struct *napi)
+ {
+ might_sleep();
++ cancel_work_sync(&napi->work);
+ if (napi_hash_del(napi))
+ synchronize_net();
+ list_del_init(&napi->dev_list);
+@@ -5578,48 +5667,18 @@ EXPORT_SYMBOL(netif_napi_del);
+
+ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
+ {
++ bool do_repoll = false;
+ void *have;
+- int work, weight;
++ int work;
+
+ list_del_init(&n->poll_list);
+
+ have = netpoll_poll_lock(n);
+
+- weight = n->weight;
+-
+- /* This NAPI_STATE_SCHED test is for avoiding a race
+- * with netpoll's poll_napi(). Only the entity which
+- * obtains the lock and sees NAPI_STATE_SCHED set will
+- * actually make the ->poll() call. Therefore we avoid
+- * accidentally calling ->poll() when NAPI is not scheduled.
+- */
+- work = 0;
+- if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+- work = n->poll(n, weight);
+- trace_napi_poll(n, work, weight);
+- }
+-
+- WARN_ON_ONCE(work > weight);
+-
+- if (likely(work < weight))
+- goto out_unlock;
++ work = __napi_poll(n, &do_repoll);
+
+- /* Drivers must not modify the NAPI state if they
+- * consume the entire weight. In such cases this code
+- * still "owns" the NAPI instance and therefore can
+- * move the instance around on the list at-will.
+- */
+- if (unlikely(napi_disable_pending(n))) {
+- napi_complete(n);
++ if (!do_repoll)
+ goto out_unlock;
+- }
+-
+- if (n->gro_list) {
+- /* flush too old packets
+- * If HZ < 1000, flush all packets.
+- */
+- napi_gro_flush(n, HZ >= 1000);
+- }
+
+ /* Some drivers may have called napi_schedule
+ * prior to exhausting their budget.
+@@ -8855,6 +8914,10 @@ static int __init net_dev_init(void)
+ sd->backlog.weight = weight_p;
+ }
+
++ napi_workq = alloc_workqueue("napi_workq", WQ_UNBOUND | WQ_HIGHPRI,
++ WQ_UNBOUND_MAX_ACTIVE | WQ_SYSFS);
++ BUG_ON(!napi_workq);
++
+ dev_boot_phase = 0;
+
+ /* The loopback device is special if any other network devices
+--- a/net/core/net-sysfs.c
++++ b/net/core/net-sysfs.c
+@@ -441,6 +441,52 @@ static ssize_t proto_down_store(struct d
+ }
+ NETDEVICE_SHOW_RW(proto_down, fmt_dec);
+
++static int change_napi_threaded(struct net_device *dev, unsigned long val)
++{
++ struct napi_struct *napi;
++
++ if (list_empty(&dev->napi_list))
++ return -EOPNOTSUPP;
++
++ list_for_each_entry(napi, &dev->napi_list, dev_list) {
++ if (val)
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ else
++ clear_bit(NAPI_STATE_THREADED, &napi->state);
++ }
++
++ return 0;
++}
++
++static ssize_t napi_threaded_store(struct device *dev,
++ struct device_attribute *attr,
++ const char *buf, size_t len)
++{
++ return netdev_store(dev, attr, buf, len, change_napi_threaded);
++}
++
++static ssize_t napi_threaded_show(struct device *dev,
++ struct device_attribute *attr,
++ char *buf)
++{
++ struct net_device *netdev = to_net_dev(dev);
++ struct napi_struct *napi;
++ bool enabled = false;
++
++ if (!rtnl_trylock())
++ return restart_syscall();
++
++ list_for_each_entry(napi, &netdev->napi_list, dev_list) {
++ if (test_bit(NAPI_STATE_THREADED, &napi->state))
++ enabled = true;
++ }
++
++ rtnl_unlock();
++
++ return sprintf(buf, fmt_dec, enabled);
++}
++static DEVICE_ATTR_RW(napi_threaded);
++
+ static ssize_t phys_port_id_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ {
+@@ -536,6 +582,7 @@ static struct attribute *net_class_attrs
+ &dev_attr_flags.attr,
+ &dev_attr_tx_queue_len.attr,
+ &dev_attr_gro_flush_timeout.attr,
++ &dev_attr_napi_threaded.attr,
+ &dev_attr_phys_port_id.attr,
+ &dev_attr_phys_port_name.attr,
+ &dev_attr_phys_switch_id.attr,
diff --git a/target/linux/generic/pending-4.19/690-net-add-support-for-threaded-NAPI-polling.patch b/target/linux/generic/pending-4.19/690-net-add-support-for-threaded-NAPI-polling.patch
new file mode 100644
index 0000000000..b5c701c80b
--- /dev/null
+++ b/target/linux/generic/pending-4.19/690-net-add-support-for-threaded-NAPI-polling.patch
@@ -0,0 +1,339 @@
+From: Felix Fietkau <nbd at nbd.name>
+Date: Sun, 26 Jul 2020 14:03:21 +0200
+Subject: [PATCH] net: add support for threaded NAPI polling
+
+For some drivers (especially 802.11 drivers), doing a lot of work in the NAPI
+poll function does not perform well. Since NAPI poll is bound to the CPU it
+was scheduled from, we can easily end up with a few very busy CPUs spending
+most of their time in softirq/ksoftirqd and some idle ones.
+
+Introduce threaded NAPI for such drivers based on a workqueue. The API is the
+same except for using netif_threaded_napi_add instead of netif_napi_add.
+
+In my tests with mt76 on MT7621 using threaded NAPI + a thread for tx scheduling
+improves LAN->WLAN bridging throughput by 10-50%. Throughput without threaded
+NAPI is wildly inconsistent, depending on the CPU that runs the tx scheduling
+thread.
+
+With threaded NAPI it seems stable and consistent (and higher than the best
+results I got without it).
+
+Based on a patch by Hillf Danton
+
+Cc: Hillf Danton <hdanton at sina.com>
+Signed-off-by: Felix Fietkau <nbd at nbd.name>
+---
+
+--- a/include/linux/netdevice.h
++++ b/include/linux/netdevice.h
+@@ -339,6 +339,7 @@ struct napi_struct {
+ struct list_head dev_list;
+ struct hlist_node napi_hash_node;
+ unsigned int napi_id;
++ struct work_struct work;
+ };
+
+ enum {
+@@ -349,6 +350,7 @@ enum {
+ NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */
+ NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */
+ NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */
++ NAPI_STATE_THREADED, /* Use threaded NAPI */
+ };
+
+ enum {
+@@ -359,6 +361,7 @@ enum {
+ NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED),
+ NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL),
+ NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL),
++ NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED),
+ };
+
+ enum gro_result {
+@@ -2230,6 +2233,26 @@ void netif_napi_add(struct net_device *d
+ int (*poll)(struct napi_struct *, int), int weight);
+
+ /**
++ * netif_threaded_napi_add - initialize a NAPI context
++ * @dev: network device
++ * @napi: NAPI context
++ * @poll: polling function
++ * @weight: default weight
++ *
++ * This variant of netif_napi_add() should be used from drivers using NAPI
++ * with CPU intensive poll functions.
++ * This will schedule polling from a high priority workqueue
++ */
++static inline void netif_threaded_napi_add(struct net_device *dev,
++ struct napi_struct *napi,
++ int (*poll)(struct napi_struct *, int),
++ int weight)
++{
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ netif_napi_add(dev, napi, poll, weight);
++}
++
++/**
+ * netif_tx_napi_add - initialize a NAPI context
+ * @dev: network device
+ * @napi: NAPI context
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -160,6 +160,7 @@ static DEFINE_SPINLOCK(offload_lock);
+ struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
+ struct list_head ptype_all __read_mostly; /* Taps */
+ static struct list_head offload_base __read_mostly;
++static struct workqueue_struct *napi_workq __read_mostly;
+
+ static int netif_rx_internal(struct sk_buff *skb);
+ static int call_netdevice_notifiers_info(unsigned long val,
+@@ -5891,6 +5892,11 @@ void __napi_schedule(struct napi_struct
+ {
+ unsigned long flags;
+
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ local_irq_save(flags);
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ local_irq_restore(flags);
+@@ -5938,6 +5944,11 @@ EXPORT_SYMBOL(napi_schedule_prep);
+ */
+ void __napi_schedule_irqoff(struct napi_struct *n)
+ {
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ }
+ EXPORT_SYMBOL(__napi_schedule_irqoff);
+@@ -6186,6 +6197,82 @@ static void init_gro_hash(struct napi_st
+ napi->gro_bitmask = 0;
+ }
+
++static int __napi_poll(struct napi_struct *n, bool *repoll)
++{
++ int work, weight;
++
++ weight = n->weight;
++
++ /* This NAPI_STATE_SCHED test is for avoiding a race
++ * with netpoll's poll_napi(). Only the entity which
++ * obtains the lock and sees NAPI_STATE_SCHED set will
++ * actually make the ->poll() call. Therefore we avoid
++ * accidentally calling ->poll() when NAPI is not scheduled.
++ */
++ work = 0;
++ if (test_bit(NAPI_STATE_SCHED, &n->state)) {
++ work = n->poll(n, weight);
++ trace_napi_poll(n, work, weight);
++ }
++
++ WARN_ON_ONCE(work > weight);
++
++ if (likely(work < weight))
++ return work;
++
++ /* Drivers must not modify the NAPI state if they
++ * consume the entire weight. In such cases this code
++ * still "owns" the NAPI instance and therefore can
++ * move the instance around on the list at-will.
++ */
++ if (unlikely(napi_disable_pending(n))) {
++ napi_complete(n);
++ return work;
++ }
++
++ if (n->gro_bitmask) {
++ /* flush too old packets
++ * If HZ < 1000, flush all packets.
++ */
++ napi_gro_flush(n, HZ >= 1000);
++ }
++
++ *repoll = true;
++
++ return work;
++}
++
++static void napi_workfn(struct work_struct *work)
++{
++ struct napi_struct *n = container_of(work, struct napi_struct, work);
++ void *have;
++
++ for (;;) {
++ bool repoll = false;
++
++ local_bh_disable();
++
++ have = netpoll_poll_lock(n);
++ __napi_poll(n, &repoll);
++ netpoll_poll_unlock(have);
++
++ local_bh_enable();
++
++ if (!repoll)
++ return;
++
++ if (!need_resched())
++ continue;
++
++ /*
++ * have to pay for the latency of task switch even if
++ * napi is scheduled
++ */
++ queue_work(napi_workq, work);
++ return;
++ }
++}
++
+ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
+ int (*poll)(struct napi_struct *, int), int weight)
+ {
+@@ -6204,6 +6291,7 @@ void netif_napi_add(struct net_device *d
+ #ifdef CONFIG_NETPOLL
+ napi->poll_owner = -1;
+ #endif
++ INIT_WORK(&napi->work, napi_workfn);
+ set_bit(NAPI_STATE_SCHED, &napi->state);
+ napi_hash_add(napi);
+ }
+@@ -6242,6 +6330,7 @@ static void flush_gro_hash(struct napi_s
+ void netif_napi_del(struct napi_struct *napi)
+ {
+ might_sleep();
++ cancel_work_sync(&napi->work);
+ if (napi_hash_del(napi))
+ synchronize_net();
+ list_del_init(&napi->dev_list);
+@@ -6254,48 +6343,18 @@ EXPORT_SYMBOL(netif_napi_del);
+
+ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
+ {
++ bool do_repoll = false;
+ void *have;
+- int work, weight;
++ int work;
+
+ list_del_init(&n->poll_list);
+
+ have = netpoll_poll_lock(n);
+
+- weight = n->weight;
+-
+- /* This NAPI_STATE_SCHED test is for avoiding a race
+- * with netpoll's poll_napi(). Only the entity which
+- * obtains the lock and sees NAPI_STATE_SCHED set will
+- * actually make the ->poll() call. Therefore we avoid
+- * accidentally calling ->poll() when NAPI is not scheduled.
+- */
+- work = 0;
+- if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+- work = n->poll(n, weight);
+- trace_napi_poll(n, work, weight);
+- }
+-
+- WARN_ON_ONCE(work > weight);
+-
+- if (likely(work < weight))
+- goto out_unlock;
++ work = __napi_poll(n, &do_repoll);
+
+- /* Drivers must not modify the NAPI state if they
+- * consume the entire weight. In such cases this code
+- * still "owns" the NAPI instance and therefore can
+- * move the instance around on the list at-will.
+- */
+- if (unlikely(napi_disable_pending(n))) {
+- napi_complete(n);
++ if (!do_repoll)
+ goto out_unlock;
+- }
+-
+- if (n->gro_bitmask) {
+- /* flush too old packets
+- * If HZ < 1000, flush all packets.
+- */
+- napi_gro_flush(n, HZ >= 1000);
+- }
+
+ /* Some drivers may have called napi_schedule
+ * prior to exhausting their budget.
+@@ -9895,6 +9954,10 @@ static int __init net_dev_init(void)
+ sd->backlog.weight = weight_p;
+ }
+
++ napi_workq = alloc_workqueue("napi_workq", WQ_UNBOUND | WQ_HIGHPRI,
++ WQ_UNBOUND_MAX_ACTIVE | WQ_SYSFS);
++ BUG_ON(!napi_workq);
++
+ dev_boot_phase = 0;
+
+ /* The loopback device is special if any other network devices
+--- a/net/core/net-sysfs.c
++++ b/net/core/net-sysfs.c
+@@ -447,6 +447,52 @@ static ssize_t proto_down_store(struct d
+ }
+ NETDEVICE_SHOW_RW(proto_down, fmt_dec);
+
++static int change_napi_threaded(struct net_device *dev, unsigned long val)
++{
++ struct napi_struct *napi;
++
++ if (list_empty(&dev->napi_list))
++ return -EOPNOTSUPP;
++
++ list_for_each_entry(napi, &dev->napi_list, dev_list) {
++ if (val)
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ else
++ clear_bit(NAPI_STATE_THREADED, &napi->state);
++ }
++
++ return 0;
++}
++
++static ssize_t napi_threaded_store(struct device *dev,
++ struct device_attribute *attr,
++ const char *buf, size_t len)
++{
++ return netdev_store(dev, attr, buf, len, change_napi_threaded);
++}
++
++static ssize_t napi_threaded_show(struct device *dev,
++ struct device_attribute *attr,
++ char *buf)
++{
++ struct net_device *netdev = to_net_dev(dev);
++ struct napi_struct *napi;
++ bool enabled = false;
++
++ if (!rtnl_trylock())
++ return restart_syscall();
++
++ list_for_each_entry(napi, &netdev->napi_list, dev_list) {
++ if (test_bit(NAPI_STATE_THREADED, &napi->state))
++ enabled = true;
++ }
++
++ rtnl_unlock();
++
++ return sprintf(buf, fmt_dec, enabled);
++}
++static DEVICE_ATTR_RW(napi_threaded);
++
+ static ssize_t phys_port_id_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ {
+@@ -542,6 +588,7 @@ static struct attribute *net_class_attrs
+ &dev_attr_flags.attr,
+ &dev_attr_tx_queue_len.attr,
+ &dev_attr_gro_flush_timeout.attr,
++ &dev_attr_napi_threaded.attr,
+ &dev_attr_phys_port_id.attr,
+ &dev_attr_phys_port_name.attr,
+ &dev_attr_phys_switch_id.attr,
diff --git a/target/linux/generic/pending-5.4/690-net-add-support-for-threaded-NAPI-polling.patch b/target/linux/generic/pending-5.4/690-net-add-support-for-threaded-NAPI-polling.patch
new file mode 100644
index 0000000000..0fd837d45e
--- /dev/null
+++ b/target/linux/generic/pending-5.4/690-net-add-support-for-threaded-NAPI-polling.patch
@@ -0,0 +1,343 @@
+From: Felix Fietkau <nbd at nbd.name>
+Date: Sun, 26 Jul 2020 14:03:21 +0200
+Subject: [PATCH] net: add support for threaded NAPI polling
+
+For some drivers (especially 802.11 drivers), doing a lot of work in the NAPI
+poll function does not perform well. Since NAPI poll is bound to the CPU it
+was scheduled from, we can easily end up with a few very busy CPUs spending
+most of their time in softirq/ksoftirqd and some idle ones.
+
+Introduce threaded NAPI for such drivers based on a workqueue. The API is the
+same except for using netif_threaded_napi_add instead of netif_napi_add.
+
+In my tests with mt76 on MT7621 using threaded NAPI + a thread for tx scheduling
+improves LAN->WLAN bridging throughput by 10-50%. Throughput without threaded
+NAPI is wildly inconsistent, depending on the CPU that runs the tx scheduling
+thread.
+
+With threaded NAPI it seems stable and consistent (and higher than the best
+results I got without it).
+
+Based on a patch by Hillf Danton
+
+Cc: Hillf Danton <hdanton at sina.com>
+Signed-off-by: Felix Fietkau <nbd at nbd.name>
+---
+
+--- a/include/linux/netdevice.h
++++ b/include/linux/netdevice.h
+@@ -340,6 +340,7 @@ struct napi_struct {
+ struct list_head dev_list;
+ struct hlist_node napi_hash_node;
+ unsigned int napi_id;
++ struct work_struct work;
+ };
+
+ enum {
+@@ -350,6 +351,7 @@ enum {
+ NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */
+ NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */
+ NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */
++ NAPI_STATE_THREADED, /* Use threaded NAPI */
+ };
+
+ enum {
+@@ -360,6 +362,7 @@ enum {
+ NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED),
+ NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL),
+ NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL),
++ NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED),
+ };
+
+ enum gro_result {
+@@ -2249,6 +2252,26 @@ void netif_napi_add(struct net_device *d
+ int (*poll)(struct napi_struct *, int), int weight);
+
+ /**
++ * netif_threaded_napi_add - initialize a NAPI context
++ * @dev: network device
++ * @napi: NAPI context
++ * @poll: polling function
++ * @weight: default weight
++ *
++ * This variant of netif_napi_add() should be used from drivers using NAPI
++ * with CPU intensive poll functions.
++ * This will schedule polling from a high priority workqueue
++ */
++static inline void netif_threaded_napi_add(struct net_device *dev,
++ struct napi_struct *napi,
++ int (*poll)(struct napi_struct *, int),
++ int weight)
++{
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ netif_napi_add(dev, napi, poll, weight);
++}
++
++/**
+ * netif_tx_napi_add - initialize a NAPI context
+ * @dev: network device
+ * @napi: NAPI context
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -156,6 +156,7 @@ static DEFINE_SPINLOCK(offload_lock);
+ struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
+ struct list_head ptype_all __read_mostly; /* Taps */
+ static struct list_head offload_base __read_mostly;
++static struct workqueue_struct *napi_workq __read_mostly;
+
+ static int netif_rx_internal(struct sk_buff *skb);
+ static int call_netdevice_notifiers_info(unsigned long val,
+@@ -5910,6 +5911,11 @@ void __napi_schedule(struct napi_struct
+ {
+ unsigned long flags;
+
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ local_irq_save(flags);
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ local_irq_restore(flags);
+@@ -5957,6 +5963,11 @@ EXPORT_SYMBOL(napi_schedule_prep);
+ */
+ void __napi_schedule_irqoff(struct napi_struct *n)
+ {
++ if (test_bit(NAPI_STATE_THREADED, &n->state)) {
++ queue_work(napi_workq, &n->work);
++ return;
++ }
++
+ ____napi_schedule(this_cpu_ptr(&softnet_data), n);
+ }
+ EXPORT_SYMBOL(__napi_schedule_irqoff);
+@@ -6218,6 +6229,84 @@ static void init_gro_hash(struct napi_st
+ napi->gro_bitmask = 0;
+ }
+
++static int __napi_poll(struct napi_struct *n, bool *repoll)
++{
++ int work, weight;
++
++ weight = n->weight;
++
++ /* This NAPI_STATE_SCHED test is for avoiding a race
++ * with netpoll's poll_napi(). Only the entity which
++ * obtains the lock and sees NAPI_STATE_SCHED set will
++ * actually make the ->poll() call. Therefore we avoid
++ * accidentally calling ->poll() when NAPI is not scheduled.
++ */
++ work = 0;
++ if (test_bit(NAPI_STATE_SCHED, &n->state)) {
++ work = n->poll(n, weight);
++ trace_napi_poll(n, work, weight);
++ }
++
++ WARN_ON_ONCE(work > weight);
++
++ if (likely(work < weight))
++ return work;
++
++ /* Drivers must not modify the NAPI state if they
++ * consume the entire weight. In such cases this code
++ * still "owns" the NAPI instance and therefore can
++ * move the instance around on the list at-will.
++ */
++ if (unlikely(napi_disable_pending(n))) {
++ napi_complete(n);
++ return work;
++ }
++
++ if (n->gro_bitmask) {
++ /* flush too old packets
++ * If HZ < 1000, flush all packets.
++ */
++ napi_gro_flush(n, HZ >= 1000);
++ }
++
++ gro_normal_list(n);
++
++ *repoll = true;
++
++ return work;
++}
++
++static void napi_workfn(struct work_struct *work)
++{
++ struct napi_struct *n = container_of(work, struct napi_struct, work);
++ void *have;
++
++ for (;;) {
++ bool repoll = false;
++
++ local_bh_disable();
++
++ have = netpoll_poll_lock(n);
++ __napi_poll(n, &repoll);
++ netpoll_poll_unlock(have);
++
++ local_bh_enable();
++
++ if (!repoll)
++ return;
++
++ if (!need_resched())
++ continue;
++
++ /*
++ * have to pay for the latency of task switch even if
++ * napi is scheduled
++ */
++ queue_work(napi_workq, work);
++ return;
++ }
++}
++
+ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
+ int (*poll)(struct napi_struct *, int), int weight)
+ {
+@@ -6238,6 +6327,7 @@ void netif_napi_add(struct net_device *d
+ #ifdef CONFIG_NETPOLL
+ napi->poll_owner = -1;
+ #endif
++ INIT_WORK(&napi->work, napi_workfn);
+ set_bit(NAPI_STATE_SCHED, &napi->state);
+ napi_hash_add(napi);
+ }
+@@ -6276,6 +6366,7 @@ static void flush_gro_hash(struct napi_s
+ void netif_napi_del(struct napi_struct *napi)
+ {
+ might_sleep();
++ cancel_work_sync(&napi->work);
+ if (napi_hash_del(napi))
+ synchronize_net();
+ list_del_init(&napi->dev_list);
+@@ -6288,50 +6379,18 @@ EXPORT_SYMBOL(netif_napi_del);
+
+ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
+ {
++ bool do_repoll = false;
+ void *have;
+- int work, weight;
++ int work;
+
+ list_del_init(&n->poll_list);
+
+ have = netpoll_poll_lock(n);
+
+- weight = n->weight;
+-
+- /* This NAPI_STATE_SCHED test is for avoiding a race
+- * with netpoll's poll_napi(). Only the entity which
+- * obtains the lock and sees NAPI_STATE_SCHED set will
+- * actually make the ->poll() call. Therefore we avoid
+- * accidentally calling ->poll() when NAPI is not scheduled.
+- */
+- work = 0;
+- if (test_bit(NAPI_STATE_SCHED, &n->state)) {
+- work = n->poll(n, weight);
+- trace_napi_poll(n, work, weight);
+- }
+-
+- WARN_ON_ONCE(work > weight);
+-
+- if (likely(work < weight))
+- goto out_unlock;
++ work = __napi_poll(n, &do_repoll);
+
+- /* Drivers must not modify the NAPI state if they
+- * consume the entire weight. In such cases this code
+- * still "owns" the NAPI instance and therefore can
+- * move the instance around on the list at-will.
+- */
+- if (unlikely(napi_disable_pending(n))) {
+- napi_complete(n);
++ if (!do_repoll)
+ goto out_unlock;
+- }
+-
+- if (n->gro_bitmask) {
+- /* flush too old packets
+- * If HZ < 1000, flush all packets.
+- */
+- napi_gro_flush(n, HZ >= 1000);
+- }
+-
+- gro_normal_list(n);
+
+ /* Some drivers may have called napi_schedule
+ * prior to exhausting their budget.
+@@ -10264,6 +10323,10 @@ static int __init net_dev_init(void)
+ sd->backlog.weight = weight_p;
+ }
+
++ napi_workq = alloc_workqueue("napi_workq", WQ_UNBOUND | WQ_HIGHPRI,
++ WQ_UNBOUND_MAX_ACTIVE | WQ_SYSFS);
++ BUG_ON(!napi_workq);
++
+ dev_boot_phase = 0;
+
+ /* The loopback device is special if any other network devices
+--- a/net/core/net-sysfs.c
++++ b/net/core/net-sysfs.c
+@@ -442,6 +442,52 @@ static ssize_t proto_down_store(struct d
+ }
+ NETDEVICE_SHOW_RW(proto_down, fmt_dec);
+
++static int change_napi_threaded(struct net_device *dev, unsigned long val)
++{
++ struct napi_struct *napi;
++
++ if (list_empty(&dev->napi_list))
++ return -EOPNOTSUPP;
++
++ list_for_each_entry(napi, &dev->napi_list, dev_list) {
++ if (val)
++ set_bit(NAPI_STATE_THREADED, &napi->state);
++ else
++ clear_bit(NAPI_STATE_THREADED, &napi->state);
++ }
++
++ return 0;
++}
++
++static ssize_t napi_threaded_store(struct device *dev,
++ struct device_attribute *attr,
++ const char *buf, size_t len)
++{
++ return netdev_store(dev, attr, buf, len, change_napi_threaded);
++}
++
++static ssize_t napi_threaded_show(struct device *dev,
++ struct device_attribute *attr,
++ char *buf)
++{
++ struct net_device *netdev = to_net_dev(dev);
++ struct napi_struct *napi;
++ bool enabled = false;
++
++ if (!rtnl_trylock())
++ return restart_syscall();
++
++ list_for_each_entry(napi, &netdev->napi_list, dev_list) {
++ if (test_bit(NAPI_STATE_THREADED, &napi->state))
++ enabled = true;
++ }
++
++ rtnl_unlock();
++
++ return sprintf(buf, fmt_dec, enabled);
++}
++static DEVICE_ATTR_RW(napi_threaded);
++
+ static ssize_t phys_port_id_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ {
+@@ -532,6 +578,7 @@ static struct attribute *net_class_attrs
+ &dev_attr_flags.attr,
+ &dev_attr_tx_queue_len.attr,
+ &dev_attr_gro_flush_timeout.attr,
++ &dev_attr_napi_threaded.attr,
+ &dev_attr_phys_port_id.attr,
+ &dev_attr_phys_port_name.attr,
+ &dev_attr_phys_switch_id.attr,
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