include/net/busy_poll.h

   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_LL_RX_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_LOWLATENCYRXPACKETS, rc);
 126
 127         } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
 128                  !need_resched() && !busy_loop_timeout(end_time));
 129
 130         rc = !skb_queue_empty(&sk->sk_receive_queue);
 131 out:
 132         rcu_read_unlock_bh();
 133         return rc;
 134 }
 135
 136 /* used in the NIC receive handler to mark the skb */
 137 static inline void skb_mark_napi_id(struct sk_buff *skb,
 138                                     struct napi_struct *napi)
 139 {
 140         skb->napi_id = napi->napi_id;
 141 }
 142
 143 /* used in the protocol hanlder to propagate the napi_id to the socket */
 144 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
 145 {
 146         sk->sk_napi_id = skb->napi_id;
 147 }
 148
 149 #else /* CONFIG_NET_LL_RX_POLL */
 150 static inline unsigned long net_busy_loop_on(void)
 151 {
 152         return 0;
 153 }
 154
 155 static inline unsigned long busy_loop_end_time(void)
 156 {
 157         return 0;
 158 }
 159
 160 static inline bool sk_can_busy_loop(struct sock *sk)
 161 {
 162         return false;
 163 }
 164
 165 static inline bool sk_busy_poll(struct sock *sk, int nonblock)
 166 {
 167         return false;
 168 }
 169
 170 static inline void skb_mark_napi_id(struct sk_buff *skb,
 171                                     struct napi_struct *napi)
 172 {
 173 }
 174
 175 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
 176 {
 177 }
 178
 179 static inline bool busy_loop_timeout(unsigned long end_time)
 180 {
 181         return true;
 182 }
 183
 184 #endif /* CONFIG_NET_LL_RX_POLL */
 185 #endif /* _LINUX_NET_BUSY_POLL_H */