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cbea8737 DS |
1 | /* |
2 | * Timer Wheel | |
3 | * Copyright (C) 2016 Cumulus Networks, Inc. | |
4 | * Donald Sharp | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, but | |
12 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * General Public License for more details. | |
15 | * | |
896014f4 DL |
16 | * You should have received a copy of the GNU General Public License along |
17 | * with this program; see the file COPYING; if not, write to the Free Software | |
18 | * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
cbea8737 DS |
19 | */ |
20 | #ifndef __WHEEL_H__ | |
21 | #define __WHEEL_H__ | |
22 | ||
23 | struct timer_wheel | |
24 | { | |
25 | struct thread_master *master; | |
26 | int slots; | |
27 | long long curr_slot; | |
28 | unsigned int period; | |
29 | unsigned int nexttime; | |
30 | unsigned int slots_to_skip; | |
31 | ||
32 | struct list **wheel_slot_lists; | |
33 | struct thread *timer; | |
34 | /* | |
35 | * Key to determine what slot the item belongs in | |
36 | */ | |
37 | unsigned int (*slot_key) (void *); | |
38 | ||
39 | void (*slot_run) (void *); | |
40 | }; | |
41 | ||
e2064401 DS |
42 | /* |
43 | * Creates a timer wheel | |
44 | * | |
45 | * master - Thread master structure for the process | |
46 | * period - The Time in seconds that the timer wheel will | |
47 | * take before it starts issuing commands again | |
48 | * for items in each slot | |
49 | * slots - The number of slots to have in this particular | |
50 | * timer wheel | |
51 | * slot_key - A hashing function of some sort that will allow | |
52 | * the timer wheel to put items into individual slots | |
53 | * slot_run - The function to run over each item in a particular slot | |
54 | * | |
55 | * Creates a timer wheel that will wake up 'slots' times over the entire | |
56 | * wheel. Each time the timer wheel wakes up it will iterate through | |
57 | * and run the slot_run function for each item stored in that particular | |
58 | * slot. | |
59 | * | |
60 | * The timer code is 'intelligent' in that it notices if anything is | |
61 | * in a particular slot and can schedule the next timer to skip | |
62 | * the empty slot. | |
63 | * | |
64 | * The general purpose of a timer wheel is to reduce events in a system. | |
65 | * A perfect example of usage for this is say hello packets that need | |
66 | * to be sent out to all your neighbors. Suppose a large routing protocol | |
67 | * has to send keepalive packets every Y seconds to each of it's peers. | |
68 | * At scale we can have a very large number of peers, X. | |
69 | * This means that we will have X timing events every Y seconds. | |
70 | * If you replace these events with a timer wheel that has Z slots | |
71 | * you will have at most Y/Z timer events if each slot has a work item | |
72 | * in it. | |
73 | * | |
74 | * When X is large the number of events in a system can quickly escalate | |
75 | * and cause significant amount of time handling thread events instead | |
76 | * of running your code. | |
77 | */ | |
cbea8737 DS |
78 | struct timer_wheel *wheel_init (struct thread_master *master, int period, size_t slots, |
79 | unsigned int (*slot_key) (void *), | |
80 | void (*slot_run) (void *)); | |
e2064401 DS |
81 | |
82 | /* | |
83 | * Delete the specified timer wheel created | |
84 | */ | |
cbea8737 DS |
85 | void wheel_delete (struct timer_wheel *); |
86 | ||
87 | /* | |
88 | * Pause the Wheel from running | |
89 | */ | |
90 | int wheel_stop (struct timer_wheel *wheel); | |
91 | ||
92 | /* | |
e2064401 | 93 | * Start the wheel running again |
cbea8737 DS |
94 | */ |
95 | int wheel_start (struct timer_wheel *wheel); | |
96 | ||
97 | /* | |
e2064401 DS |
98 | * wheel - The Timer wheel being modified |
99 | * item - The generic data structure that will be handed | |
100 | * to the slot_run function. | |
101 | * | |
cbea8737 DS |
102 | * Add item to a slot setup by the slot_key, |
103 | * possibly change next time pop. | |
104 | */ | |
105 | int wheel_add_item (struct timer_wheel *wheel, void *item); | |
106 | ||
107 | /* | |
e2064401 DS |
108 | * wheel - The Timer wheel being modified. |
109 | * item - The item to remove from one of the slots in | |
110 | * the timer wheel. | |
111 | * | |
cbea8737 DS |
112 | * Remove a item to a slot setup by the slot_key, |
113 | * possibly change next time pop. | |
114 | */ | |
115 | int wheel_remove_item (struct timer_wheel *wheel, void *item); | |
116 | ||
117 | #endif |