0002-Added-knapid-kernel-threads.patch

From 5d9be44de0af4161526cbc805a7ddbc66a8e5966 Mon Sep 17 00:00:00 2001
From: Riccardo Mancini <r.mancini@santannapisa.it>
Date: Sun, 23 Jun 2019 19:53:45 +0200
Subject: [PATCH 2/4] Added knapid kernel threads

The threads are created using the  cpu hotplug interface
in smpboot.h
---
 net/core/dev.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 007f3e15836a..a195a3a4e53e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -142,6 +142,8 @@
 #include <linux/net_namespace.h>
 #include <linux/indirect_call_wrapper.h>
 #include <net/devlink.h>
+#include <linux/kthread.h>
+#include <linux/smpboot.h>
 
 #include "net-sysfs.h"
 
@@ -164,6 +166,16 @@ static int call_netdevice_notifiers_extack(unsigned long val,
 					   struct netlink_ext_ack *extack);
 static struct napi_struct *napi_by_id(unsigned int napi_id);
 
+
+#ifdef CONFIG_THREADED_NAPI
+
+int knapid_enabled __read_mostly = 1;
+
+DEFINE_PER_CPU(struct task_struct *, knapid);
+DEFINE_PER_CPU(int, napi_running);
+
+#endif
+
 /*
  * The @dev_base_head list is protected by @dev_base_lock and the rtnl
  * semaphore.
@@ -3974,6 +3986,34 @@ int dev_tx_weight __read_mostly = 64;
 
 #ifdef CONFIG_THREADED_NAPI
 
+static inline void wakeup_napid(void)
+{
+	/* Interrupts are disabled: no need to stop preemption */
+	struct task_struct *tsk = __this_cpu_read(knapid);
+
+	if (tsk && tsk->state != TASK_RUNNING)
+		wake_up_process(tsk);
+}
+
+static inline int napid_running(void)
+{
+	/* Interrupts are disabled: no need to stop preemption */
+	struct task_struct *tsk = __this_cpu_read(knapid);
+
+	return tsk && tsk->state == TASK_RUNNING;
+}
+
+/* Called with irq disabled */
+static inline void ______napi_schedule(void)
+{
+	if (!knapid_enabled){
+		__raise_softirq_irqoff(NET_RX_SOFTIRQ);
+	} else{
+		wakeup_napid();
+	}
+	
+}
+
 #else
 
 /* Called with irq disabled */
@@ -6435,6 +6475,39 @@ static __latent_entropy int napi_poll_everything(void)
 
 #ifdef CONFIG_THREADED_NAPI
 
+static void net_rx_action(struct softirq_action *h)
+{
+	if (napi_poll_everything()){
+		// I still have work to do
+		if (!knapid_enabled)
+			raise_softirq(NET_RX_SOFTIRQ);
+	}
+}
+
+static void run_knapid(unsigned int cpu){
+	napi_poll_everything();
+}
+
+static int knapid_should_run(unsigned int cpu)
+{
+	int ret;
+	struct softnet_data *sd;
+	
+	local_irq_disable();
+	sd = this_cpu_ptr(&softnet_data);
+	ret = !list_empty(&sd->poll_list);
+	local_irq_enable();
+
+	if (ret){
+		// I still have work to do
+		if (!knapid_enabled){
+			return 0;
+		} else
+			return 1;
+	} else
+		return 0;
+}
+
 #else
 
 static void net_rx_action(struct softirq_action *h)
@@ -9795,6 +9868,17 @@ static struct pernet_operations __net_initdata default_device_ops = {
  *
  */
 
+#ifdef CONFIG_THREADED_NAPI
+
+static struct smp_hotplug_thread napi_threads = {
+	.store			= &knapid,
+	.thread_should_run	= knapid_should_run,
+	.thread_fn		= run_knapid,
+	.thread_comm		= "knapid/%u",
+};
+
+#endif
+
 /*
  *       This is called single threaded during boot, so no need
  *       to take the rtnl semaphore.
@@ -9868,6 +9952,11 @@ static int __init net_dev_init(void)
 	open_softirq(NET_TX_SOFTIRQ, net_tx_action);
 	open_softirq(NET_RX_SOFTIRQ, net_rx_action);
 
+#ifdef CONFIG_THREADED_NAPI
+	this_cpu_write(napi_running, 0);
+	BUG_ON(smpboot_register_percpu_thread(&napi_threads));
+#endif
+
 	rc = cpuhp_setup_state_nocalls(CPUHP_NET_DEV_DEAD, "net/dev:dead",
 				       NULL, dev_cpu_dead);
 	WARN_ON(rc < 0);
-- 
2.21.0