Adding upstream version 9.1.upstream/9.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 103 insertions, 0 deletions

diff --git a/lib/wheel.h b/lib/wheel.h
new file mode 100644
index 0000000..0d9ac10
--- /dev/null
+++ b/lib/wheel.h
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Timer Wheel
+ * Copyright (C) 2016 Cumulus Networks, Inc.
+ * Donald Sharp
+ */
+#ifndef __WHEEL_H__
+#define __WHEEL_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct timer_wheel {
+	char *name;
+	struct event_loop *master;
+	int slots;
+	long long curr_slot;
+	unsigned int period;
+	unsigned int nexttime;
+	unsigned int slots_to_skip;
+
+	struct list **wheel_slot_lists;
+	struct event *timer;
+	/*
+	 * Key to determine what slot the item belongs in
+	 */
+	unsigned int (*slot_key)(const void *);
+
+	void (*slot_run)(void *);
+};
+
+/*
+ * Creates a timer wheel
+ *
+ * master - Thread master structure for the process
+ * period - The Time in seconds that the timer wheel will
+ *          take before it starts issuing commands again
+ *          for items in each slot
+ * slots  - The number of slots to have in this particular
+ *          timer wheel
+ * slot_key - A hashing function of some sort that will allow
+ *            the timer wheel to put items into individual slots
+ * slot_run - The function to run over each item in a particular slot
+ *
+ * Creates a timer wheel that will wake up 'slots' times over the entire
+ * wheel.  Each time the timer wheel wakes up it will iterate through
+ * and run the slot_run function for each item stored in that particular
+ * slot.
+ *
+ * The timer code is 'intelligent' in that it notices if anything is
+ * in a particular slot and can schedule the next timer to skip
+ * the empty slot.
+ *
+ * The general purpose of a timer wheel is to reduce events in a system.
+ * A perfect example of usage for this is say hello packets that need
+ * to be sent out to all your neighbors.  Suppose a large routing protocol
+ * has to send keepalive packets every Y seconds to each of it's peers.
+ * At scale we can have a very large number of peers, X.
+ * This means that we will have X timing events every Y seconds.
+ * If you replace these events with a timer wheel that has Z slots
+ * you will have at most Y/Z timer events if each slot has a work item
+ * in it.
+ *
+ * When X is large the number of events in a system can quickly escalate
+ * and cause significant amount of time handling thread events instead
+ * of running your code.
+ */
+struct timer_wheel *wheel_init(struct event_loop *master, int period,
+			       size_t slots,
+			       unsigned int (*slot_key)(const void *),
+			       void (*slot_run)(void *), const char *run_name);
+
+/*
+ * Delete the specified timer wheel created
+ */
+void wheel_delete(struct timer_wheel *);
+
+/*
+ * wheel - The Timer wheel being modified
+ * item - The generic data structure that will be handed
+ *        to the slot_run function.
+ *
+ * Add item to a slot setup by the slot_key,
+ * possibly change next time pop.
+ */
+int wheel_add_item(struct timer_wheel *wheel, void *item);
+
+/*
+ * wheel - The Timer wheel being modified.
+ * item - The item to remove from one of the slots in
+ *        the timer wheel.
+ *
+ * Remove a item to a slot setup by the slot_key,
+ * possibly change next time pop.
+ */
+int wheel_remove_item(struct timer_wheel *wheel, void *item);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif