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06021292 ET |
1 | /* |
2 | * Low Latency Sockets | |
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 | /* | |
25 | * For now this depends on CONFIG_X86_TSC | |
26 | */ | |
27 | ||
28 | #ifndef _LINUX_NET_LL_POLL_H | |
29 | #define _LINUX_NET_LL_POLL_H | |
30 | ||
31 | #include <linux/netdevice.h> | |
32 | #include <net/ip.h> | |
33 | ||
34 | #ifdef CONFIG_NET_LL_RX_POLL | |
35 | ||
36 | struct napi_struct; | |
37 | extern unsigned long sysctl_net_ll_poll __read_mostly; | |
38 | ||
39 | /* return values from ndo_ll_poll */ | |
40 | #define LL_FLUSH_FAILED -1 | |
41 | #define LL_FLUSH_BUSY -2 | |
42 | ||
43 | /* we don't mind a ~2.5% imprecision */ | |
44 | #define TSC_MHZ (tsc_khz >> 10) | |
45 | ||
46 | static inline cycles_t ll_end_time(void) | |
47 | { | |
48 | return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles(); | |
49 | } | |
50 | ||
51 | static inline bool sk_valid_ll(struct sock *sk) | |
52 | { | |
53 | return sysctl_net_ll_poll && sk->sk_napi_id && | |
54 | !need_resched() && !signal_pending(current); | |
55 | } | |
56 | ||
57 | static inline bool can_poll_ll(cycles_t end_time) | |
58 | { | |
59 | return !time_after((unsigned long)get_cycles(), | |
60 | (unsigned long)end_time); | |
61 | } | |
62 | ||
63 | static inline bool sk_poll_ll(struct sock *sk, int nonblock) | |
64 | { | |
65 | cycles_t end_time = ll_end_time(); | |
66 | const struct net_device_ops *ops; | |
67 | struct napi_struct *napi; | |
68 | int rc = false; | |
69 | ||
70 | /* | |
71 | * rcu read lock for napi hash | |
72 | * bh so we don't race with net_rx_action | |
73 | */ | |
74 | rcu_read_lock_bh(); | |
75 | ||
76 | napi = napi_by_id(sk->sk_napi_id); | |
77 | if (!napi) | |
78 | goto out; | |
79 | ||
80 | ops = napi->dev->netdev_ops; | |
81 | if (!ops->ndo_ll_poll) | |
82 | goto out; | |
83 | ||
84 | do { | |
85 | ||
86 | rc = ops->ndo_ll_poll(napi); | |
87 | ||
88 | if (rc == LL_FLUSH_FAILED) | |
89 | break; /* permanent failure */ | |
90 | ||
91 | if (rc > 0) | |
92 | /* local bh are disabled so it is ok to use _BH */ | |
93 | NET_ADD_STATS_BH(sock_net(sk), | |
94 | LINUX_MIB_LOWLATENCYRXPACKETS, rc); | |
95 | ||
96 | } while (skb_queue_empty(&sk->sk_receive_queue) | |
97 | && can_poll_ll(end_time) && !nonblock); | |
98 | ||
99 | rc = !skb_queue_empty(&sk->sk_receive_queue); | |
100 | out: | |
101 | rcu_read_unlock_bh(); | |
102 | return rc; | |
103 | } | |
104 | ||
105 | /* used in the NIC receive handler to mark the skb */ | |
106 | static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi) | |
107 | { | |
108 | skb->napi_id = napi->napi_id; | |
109 | } | |
110 | ||
111 | /* used in the protocol hanlder to propagate the napi_id to the socket */ | |
112 | static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb) | |
113 | { | |
114 | sk->sk_napi_id = skb->napi_id; | |
115 | } | |
116 | ||
117 | #else /* CONFIG_NET_LL_RX_POLL */ | |
118 | ||
119 | static inline cycles_t ll_end_time(void) | |
120 | { | |
121 | return 0; | |
122 | } | |
123 | ||
124 | static inline bool sk_valid_ll(struct sock *sk) | |
125 | { | |
126 | return false; | |
127 | } | |
128 | ||
129 | static inline bool sk_poll_ll(struct sock *sk, int nonblock) | |
130 | { | |
131 | return false; | |
132 | } | |
133 | ||
134 | static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi) | |
135 | { | |
136 | } | |
137 | ||
138 | static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb) | |
139 | { | |
140 | } | |
141 | ||
142 | static inline bool can_poll_ll(cycles_t end_time) | |
143 | { | |
144 | return false; | |
145 | } | |
146 | ||
147 | #endif /* CONFIG_NET_LL_RX_POLL */ | |
148 | #endif /* _LINUX_NET_LL_POLL_H */ |