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git.proxmox.com Git - mirror_frr.git/blob - lib/wheel.h
3 * Copyright (C) 2016 Cumulus Networks, Inc.
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.
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.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; see the file COPYING; if not, write to the
18 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
26 struct thread_master
*master
;
30 unsigned int nexttime
;
31 unsigned int slots_to_skip
;
33 struct list
**wheel_slot_lists
;
36 * Key to determine what slot the item belongs in
38 unsigned int (*slot_key
) (void *);
40 void (*slot_run
) (void *);
44 * Creates a timer wheel
46 * master - Thread master structure for the process
47 * period - The Time in seconds that the timer wheel will
48 * take before it starts issuing commands again
49 * for items in each slot
50 * slots - The number of slots to have in this particular
52 * slot_key - A hashing function of some sort that will allow
53 * the timer wheel to put items into individual slots
54 * slot_run - The function to run over each item in a particular slot
56 * Creates a timer wheel that will wake up 'slots' times over the entire
57 * wheel. Each time the timer wheel wakes up it will iterate through
58 * and run the slot_run function for each item stored in that particular
61 * The timer code is 'intelligent' in that it notices if anything is
62 * in a particular slot and can schedule the next timer to skip
65 * The general purpose of a timer wheel is to reduce events in a system.
66 * A perfect example of usage for this is say hello packets that need
67 * to be sent out to all your neighbors. Suppose a large routing protocol
68 * has to send keepalive packets every Y seconds to each of it's peers.
69 * At scale we can have a very large number of peers, X.
70 * This means that we will have X timing events every Y seconds.
71 * If you replace these events with a timer wheel that has Z slots
72 * you will have at most Y/Z timer events if each slot has a work item
75 * When X is large the number of events in a system can quickly escalate
76 * and cause significant amount of time handling thread events instead
77 * of running your code.
79 struct timer_wheel
*wheel_init (struct thread_master
*master
, int period
, size_t slots
,
80 unsigned int (*slot_key
) (void *),
81 void (*slot_run
) (void *));
84 * Delete the specified timer wheel created
86 void wheel_delete (struct timer_wheel
*);
89 * Pause the Wheel from running
91 int wheel_stop (struct timer_wheel
*wheel
);
94 * Start the wheel running again
96 int wheel_start (struct timer_wheel
*wheel
);
99 * wheel - The Timer wheel being modified
100 * item - The generic data structure that will be handed
101 * to the slot_run function.
103 * Add item to a slot setup by the slot_key,
104 * possibly change next time pop.
106 int wheel_add_item (struct timer_wheel
*wheel
, void *item
);
109 * wheel - The Timer wheel being modified.
110 * item - The item to remove from one of the slots in
113 * Remove a item to a slot setup by the slot_key,
114 * possibly change next time pop.
116 int wheel_remove_item (struct timer_wheel
*wheel
, void *item
);