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d8b87afe7c
It doesn't make much sense for a hash function to modify its argument, so const the hash input. BGP does it in a couple places, those cast away the const. Not great but not any worse than it was. Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
127 lines
3.9 KiB
C
127 lines
3.9 KiB
C
/*
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* Timer Wheel
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* Copyright (C) 2016 Cumulus Networks, Inc.
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* Donald Sharp
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; see the file COPYING; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef __WHEEL_H__
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#define __WHEEL_H__
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct timer_wheel {
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char *name;
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struct thread_master *master;
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int slots;
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long long curr_slot;
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unsigned int period;
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unsigned int nexttime;
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unsigned int slots_to_skip;
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struct list **wheel_slot_lists;
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struct thread *timer;
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/*
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* Key to determine what slot the item belongs in
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*/
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unsigned int (*slot_key)(const void *);
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void (*slot_run)(void *);
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};
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/*
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* Creates a timer wheel
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*
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* master - Thread master structure for the process
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* period - The Time in seconds that the timer wheel will
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* take before it starts issuing commands again
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* for items in each slot
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* slots - The number of slots to have in this particular
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* timer wheel
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* slot_key - A hashing function of some sort that will allow
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* the timer wheel to put items into individual slots
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* slot_run - The function to run over each item in a particular slot
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*
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* Creates a timer wheel that will wake up 'slots' times over the entire
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* wheel. Each time the timer wheel wakes up it will iterate through
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* and run the slot_run function for each item stored in that particular
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* slot.
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*
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* The timer code is 'intelligent' in that it notices if anything is
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* in a particular slot and can schedule the next timer to skip
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* the empty slot.
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*
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* The general purpose of a timer wheel is to reduce events in a system.
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* A perfect example of usage for this is say hello packets that need
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* to be sent out to all your neighbors. Suppose a large routing protocol
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* has to send keepalive packets every Y seconds to each of it's peers.
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* At scale we can have a very large number of peers, X.
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* This means that we will have X timing events every Y seconds.
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* If you replace these events with a timer wheel that has Z slots
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* you will have at most Y/Z timer events if each slot has a work item
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* in it.
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*
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* When X is large the number of events in a system can quickly escalate
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* and cause significant amount of time handling thread events instead
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* of running your code.
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*/
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struct timer_wheel *wheel_init(struct thread_master *master, int period,
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size_t slots,
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unsigned int (*slot_key)(const void *),
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void (*slot_run)(void *), const char *run_name);
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/*
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* Delete the specified timer wheel created
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*/
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void wheel_delete(struct timer_wheel *);
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/*
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* Pause the Wheel from running
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*/
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int wheel_stop(struct timer_wheel *wheel);
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/*
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* Start the wheel running again
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*/
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int wheel_start(struct timer_wheel *wheel);
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/*
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* wheel - The Timer wheel being modified
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* item - The generic data structure that will be handed
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* to the slot_run function.
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*
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* Add item to a slot setup by the slot_key,
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* possibly change next time pop.
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*/
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int wheel_add_item(struct timer_wheel *wheel, void *item);
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/*
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* wheel - The Timer wheel being modified.
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* item - The item to remove from one of the slots in
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* the timer wheel.
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*
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* Remove a item to a slot setup by the slot_key,
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* possibly change next time pop.
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*/
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int wheel_remove_item(struct timer_wheel *wheel, void *item);
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#ifdef __cplusplus
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}
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#endif
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#endif
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