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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 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
29 struct thread_master
*master
;
33 unsigned int nexttime
;
34 unsigned int slots_to_skip
;
36 struct list
**wheel_slot_lists
;
39 * Key to determine what slot the item belongs in
41 unsigned int (*slot_key
)(const void *);
43 void (*slot_run
)(void *);
47 * Creates a timer wheel
49 * master - Thread master structure for the process
50 * period - The Time in seconds that the timer wheel will
51 * take before it starts issuing commands again
52 * for items in each slot
53 * slots - The number of slots to have in this particular
55 * slot_key - A hashing function of some sort that will allow
56 * the timer wheel to put items into individual slots
57 * slot_run - The function to run over each item in a particular slot
59 * Creates a timer wheel that will wake up 'slots' times over the entire
60 * wheel. Each time the timer wheel wakes up it will iterate through
61 * and run the slot_run function for each item stored in that particular
64 * The timer code is 'intelligent' in that it notices if anything is
65 * in a particular slot and can schedule the next timer to skip
68 * The general purpose of a timer wheel is to reduce events in a system.
69 * A perfect example of usage for this is say hello packets that need
70 * to be sent out to all your neighbors. Suppose a large routing protocol
71 * has to send keepalive packets every Y seconds to each of it's peers.
72 * At scale we can have a very large number of peers, X.
73 * This means that we will have X timing events every Y seconds.
74 * If you replace these events with a timer wheel that has Z slots
75 * you will have at most Y/Z timer events if each slot has a work item
78 * When X is large the number of events in a system can quickly escalate
79 * and cause significant amount of time handling thread events instead
80 * of running your code.
82 struct timer_wheel
*wheel_init(struct thread_master
*master
, int period
,
84 unsigned int (*slot_key
)(const void *),
85 void (*slot_run
)(void *), const char *run_name
);
88 * Delete the specified timer wheel created
90 void wheel_delete(struct timer_wheel
*);
93 * Pause the Wheel from running
95 int wheel_stop(struct timer_wheel
*wheel
);
98 * Start the wheel running again
100 int wheel_start(struct timer_wheel
*wheel
);
103 * wheel - The Timer wheel being modified
104 * item - The generic data structure that will be handed
105 * to the slot_run function.
107 * Add item to a slot setup by the slot_key,
108 * possibly change next time pop.
110 int wheel_add_item(struct timer_wheel
*wheel
, void *item
);
113 * wheel - The Timer wheel being modified.
114 * item - The item to remove from one of the slots in
117 * Remove a item to a slot setup by the slot_key,
118 * possibly change next time pop.
120 int wheel_remove_item(struct timer_wheel
*wheel
, void *item
);