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_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 static inline u64 busy_loop_us_clock(void)
  46 {
  47         return local_clock() >> 10;
  48 }
  49
  50 static inline unsigned long sk_busy_loop_end_time(struct sock *sk)
  51 {
  52         return busy_loop_us_clock() + ACCESS_ONCE(sk->sk_ll_usec);
  53 }
  54
  55 /* in poll/select we use the global sysctl_net_ll_poll value */
  56 static inline unsigned long busy_loop_end_time(void)
  57 {
  58         return busy_loop_us_clock() + ACCESS_ONCE(sysctl_net_busy_poll);
  59 }
  60
  61 static inline bool sk_can_busy_loop(struct sock *sk)
  62 {
  63         return sk->sk_ll_usec && sk->sk_napi_id &&
  64                !need_resched() && !signal_pending(current);
  65 }
  66
  67
  68 static inline bool busy_loop_timeout(unsigned long end_time)
  69 {
  70         unsigned long now = busy_loop_us_clock();
  71
  72         return time_after(now, end_time);
  73 }
  74
  75 /* when used in sock_poll() nonblock is known at compile time to be true
  76  * so the loop and end_time will be optimized out
  77  */
  78 static inline bool sk_busy_loop(struct sock *sk, int nonblock)
  79 {
  80         unsigned long end_time = !nonblock ? sk_busy_loop_end_time(sk) : 0;
  81         const struct net_device_ops *ops;
  82         struct napi_struct *napi;
  83         int rc = false;
  84
  85         /*
  86          * rcu read lock for napi hash
  87          * bh so we don't race with net_rx_action
  88          */
  89         rcu_read_lock_bh();
  90
  91         napi = napi_by_id(sk->sk_napi_id);
  92         if (!napi)
  93                 goto out;
  94
  95         ops = napi->dev->netdev_ops;
  96         if (!ops->ndo_busy_poll)
  97                 goto out;
  98
  99         do {
 100                 rc = ops->ndo_busy_poll(napi);
 101
 102                 if (rc == LL_FLUSH_FAILED)
 103                         break; /* permanent failure */
 104
 105                 if (rc > 0)
 106                         /* local bh are disabled so it is ok to use _BH */
 107                         NET_ADD_STATS_BH(sock_net(sk),
 108                                          LINUX_MIB_BUSYPOLLRXPACKETS, rc);
 109                 cpu_relax();
 110
 111         } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
 112                  !need_resched() && !busy_loop_timeout(end_time));
 113
 114         rc = !skb_queue_empty(&sk->sk_receive_queue);
 115 out:
 116         rcu_read_unlock_bh();
 117         return rc;
 118 }
 119
 120 /* used in the NIC receive handler to mark the skb */
 121 static inline void skb_mark_napi_id(struct sk_buff *skb,
 122                                     struct napi_struct *napi)
 123 {
 124         skb->napi_id = napi->napi_id;
 125 }
 126
 127 /* used in the protocol hanlder to propagate the napi_id to the socket */
 128 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
 129 {
 130         sk->sk_napi_id = skb->napi_id;
 131 }
 132
 133 #else /* CONFIG_NET_RX_BUSY_POLL */
 134 static inline unsigned long net_busy_loop_on(void)
 135 {
 136         return 0;
 137 }
 138
 139 static inline unsigned long busy_loop_end_time(void)
 140 {
 141         return 0;
 142 }
 143
 144 static inline bool sk_can_busy_loop(struct sock *sk)
 145 {
 146         return false;
 147 }
 148
 149 static inline void skb_mark_napi_id(struct sk_buff *skb,
 150                                     struct napi_struct *napi)
 151 {
 152 }
 153
 154 static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
 155 {
 156 }
 157
 158 static inline bool busy_loop_timeout(unsigned long end_time)
 159 {
 160         return true;
 161 }
 162
 163 static inline bool sk_busy_loop(struct sock *sk, int nonblock)
 164 {
 165         return false;
 166 }
 167
 168 #endif /* CONFIG_NET_RX_BUSY_POLL */
 169 #endif /* _LINUX_NET_BUSY_POLL_H */