diff options
Diffstat (limited to 'target/linux/generic/pending-5.10/690-net-add-support-for-threaded-NAPI-polling.patch')
| -rw-r--r-- | target/linux/generic/pending-5.10/690-net-add-support-for-threaded-NAPI-polling.patch | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/target/linux/generic/pending-5.10/690-net-add-support-for-threaded-NAPI-polling.patch b/target/linux/generic/pending-5.10/690-net-add-support-for-threaded-NAPI-polling.patch new file mode 100644 index 0000000000..79b7832f2a --- /dev/null +++ b/target/linux/generic/pending-5.10/690-net-add-support-for-threaded-NAPI-polling.patch @@ -0,0 +1,284 @@ +From: Felix Fietkau <nbd@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, throughput 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@sina.com> +Signed-off-by: Felix Fietkau <nbd@nbd.name> +--- + +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -347,6 +347,7 @@ struct napi_struct { + struct list_head dev_list; + struct hlist_node napi_hash_node; + unsigned int napi_id; ++ struct work_struct work; + }; + + enum { +@@ -357,6 +358,7 @@ enum { + NAPI_STATE_LISTED, /* NAPI added to system lists */ + 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 { +@@ -367,6 +369,7 @@ enum { + NAPIF_STATE_LISTED = BIT(NAPI_STATE_LISTED), + 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 { +@@ -2411,6 +2414,26 @@ 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 +@@ -159,6 +159,7 @@ 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, +@@ -6404,6 +6405,11 @@ 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); +@@ -6451,6 +6457,11 @@ 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); +@@ -6712,6 +6723,86 @@ 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); ++ } ++ ++ if (unlikely(work > weight)) ++ pr_err_once("NAPI poll function %pS returned %d, exceeding its budget of %d.\n", ++ n->poll, 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) + { +@@ -6735,6 +6826,7 @@ 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); + set_bit(NAPI_STATE_NPSVC, &napi->state); + list_add_rcu(&napi->dev_list, &dev->napi_list); +@@ -6777,6 +6869,7 @@ void __netif_napi_del(struct napi_struct + if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state)) + return; + ++ cancel_work_sync(&napi->work); + napi_hash_del(napi); + list_del_rcu(&napi->dev_list); + napi_free_frags(napi); +@@ -6788,52 +6881,18 @@ 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); +- } +- +- if (unlikely(work > weight)) +- pr_err_once("NAPI poll function %pS returned %d, exceeding its budget of %d.\n", +- n->poll, 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. +@@ -11288,6 +11347,10 @@ 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 |