1 /* 2 * net busy poll support 3 * Copyright(c) 2013 Intel Corporation. 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms and conditions of the GNU General Public License, 7 * version 2, as published by the Free Software Foundation. 8 * 9 * This program is distributed in the hope it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 12 * more details. 13 * 14 * You should have received a copy of the GNU General Public License along with 15 * this program; if not, write to the Free Software Foundation, Inc., 16 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Author: Eliezer Tamir 19 * 20 * Contact Information: 21 * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net> 22 */ 23 24 #ifndef _LINUX_NET_BUSY_POLL_H 25 #define _LINUX_NET_BUSY_POLL_H 26 27 #include <linux/netdevice.h> 28 #include <net/ip.h> 29 30 #ifdef CONFIG_NET_RX_BUSY_POLL 31 32 struct napi_struct; 33 extern unsigned int sysctl_net_busy_read __read_mostly; 34 extern unsigned int sysctl_net_busy_poll __read_mostly; 35 36 /* return values from ndo_ll_poll */ 37 #define LL_FLUSH_FAILED -1 38 #define LL_FLUSH_BUSY -2 39 40 static inline bool net_busy_loop_on(void) 41 { 42 return sysctl_net_busy_poll; 43 } 44 45 /* a wrapper to make debug_smp_processor_id() happy 46 * we can use sched_clock() because we don't care much about precision 47 * we only care that the average is bounded 48 */ 49 #ifdef CONFIG_DEBUG_PREEMPT 50 static inline u64 busy_loop_us_clock(void) 51 { 52 u64 rc; 53 54 preempt_disable_notrace(); 55 rc = sched_clock(); 56 preempt_enable_no_resched_notrace(); 57 58 return rc >> 10; 59 } 60 #else /* CONFIG_DEBUG_PREEMPT */ 61 static inline u64 busy_loop_us_clock(void) 62 { 63 return sched_clock() >> 10; 64 } 65 #endif /* CONFIG_DEBUG_PREEMPT */ 66 67 static inline unsigned long sk_busy_loop_end_time(struct sock *sk) 68 { 69 return busy_loop_us_clock() + ACCESS_ONCE(sk->sk_ll_usec); 70 } 71 72 /* in poll/select we use the global sysctl_net_ll_poll value */ 73 static inline unsigned long busy_loop_end_time(void) 74 { 75 return busy_loop_us_clock() + ACCESS_ONCE(sysctl_net_busy_poll); 76 } 77 78 static inline bool sk_can_busy_loop(struct sock *sk) 79 { 80 return sk->sk_ll_usec && sk->sk_napi_id && 81 !need_resched() && !signal_pending(current); 82 } 83 84 85 static inline bool busy_loop_timeout(unsigned long end_time) 86 { 87 unsigned long now = busy_loop_us_clock(); 88 89 return time_after(now, end_time); 90 } 91 92 /* when used in sock_poll() nonblock is known at compile time to be true 93 * so the loop and end_time will be optimized out 94 */ 95 static inline bool sk_busy_loop(struct sock *sk, int nonblock) 96 { 97 unsigned long end_time = !nonblock ? sk_busy_loop_end_time(sk) : 0; 98 const struct net_device_ops *ops; 99 struct napi_struct *napi; 100 int rc = false; 101 102 /* 103 * rcu read lock for napi hash 104 * bh so we don't race with net_rx_action 105 */ 106 rcu_read_lock_bh(); 107 108 napi = napi_by_id(sk->sk_napi_id); 109 if (!napi) 110 goto out; 111 112 ops = napi->dev->netdev_ops; 113 if (!ops->ndo_busy_poll) 114 goto out; 115 116 do { 117 rc = ops->ndo_busy_poll(napi); 118 119 if (rc == LL_FLUSH_FAILED) 120 break; /* permanent failure */ 121 122 if (rc > 0) 123 /* local bh are disabled so it is ok to use _BH */ 124 NET_ADD_STATS_BH(sock_net(sk), 125 LINUX_MIB_BUSYPOLLRXPACKETS, rc); 126 cpu_relax(); 127 128 } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) && 129 !need_resched() && !busy_loop_timeout(end_time)); 130 131 rc = !skb_queue_empty(&sk->sk_receive_queue); 132 out: 133 rcu_read_unlock_bh(); 134 return rc; 135 } 136 137 /* used in the NIC receive handler to mark the skb */ 138 static inline void skb_mark_napi_id(struct sk_buff *skb, 139 struct napi_struct *napi) 140 { 141 skb->napi_id = napi->napi_id; 142 } 143 144 /* used in the protocol hanlder to propagate the napi_id to the socket */ 145 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb) 146 { 147 sk->sk_napi_id = skb->napi_id; 148 } 149 150 #else /* CONFIG_NET_RX_BUSY_POLL */ 151 static inline unsigned long net_busy_loop_on(void) 152 { 153 return 0; 154 } 155 156 static inline unsigned long busy_loop_end_time(void) 157 { 158 return 0; 159 } 160 161 static inline bool sk_can_busy_loop(struct sock *sk) 162 { 163 return false; 164 } 165 166 static inline void skb_mark_napi_id(struct sk_buff *skb, 167 struct napi_struct *napi) 168 { 169 } 170 171 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb) 172 { 173 } 174 175 static inline bool busy_loop_timeout(unsigned long end_time) 176 { 177 return true; 178 } 179 180 static inline bool sk_busy_loop(struct sock *sk, int nonblock) 181 { 182 return false; 183 } 184 185 #endif /* CONFIG_NET_RX_BUSY_POLL */ 186 #endif /* _LINUX_NET_BUSY_POLL_H */ 187