zebra, lib: fix the ZEBRA_INTERFACE_VRF_UPDATE zapi message

[mirror_frr.git] / lib / wheel.h

diff --git a/lib/wheel.h b/lib/wheel.h
index ddb79988b4b4f18aa56e5ef0d70a6bd379ec254a..c8e83fafcb81ea3f4753121d0158554f754276ad 100644 (file)
--- a/lib/wheel.h
+++ b/lib/wheel.h
@@ -13,58 +13,106 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program; see the file COPYING; if not, write to the
- * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
- * MA 02110-1301 USA
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #ifndef __WHEEL_H__
 #define __WHEEL_H__
 
-struct timer_wheel
-{
-  struct thread_master *master;
-  int slots;
-  long long curr_slot;
-  unsigned int period;
-  unsigned int nexttime;
-  unsigned int slots_to_skip;
+struct timer_wheel {
+       char *name;
+       struct thread_master *master;
+       int slots;
+       long long curr_slot;
+       unsigned int period;
+       unsigned int nexttime;
+       unsigned int slots_to_skip;
 
-  struct list **wheel_slot_lists;
-  struct thread *timer;
-  /*
-   * Key to determine what slot the item belongs in
-   */
-  unsigned int (*slot_key) (void *);
+       struct list **wheel_slot_lists;
+       struct thread *timer;
+       /*
+        * Key to determine what slot the item belongs in
+        */
+       unsigned int (*slot_key)(void *);
 
-  void (*slot_run) (void *);
+       void (*slot_run)(void *);
 };
 
-struct timer_wheel *wheel_init (struct thread_master *master, int period, size_t slots,
-                               unsigned int (*slot_key) (void *),
-                               void (*slot_run) (void *));
-void wheel_delete (struct timer_wheel *);
+/*
+ * 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 thread_master *master, int period,
+                              size_t slots, unsigned int (*slot_key)(void *),
+                              void (*slot_run)(void *),
+                              const char *run_name);
+
+/*
+ * Delete the specified timer wheel created
+ */
+void wheel_delete(struct timer_wheel *);
 
 /*
  * Pause the Wheel from running
  */
-int wheel_stop (struct timer_wheel *wheel);
+int wheel_stop(struct timer_wheel *wheel);
 
 /*
- * Start the wheel from running again
+ * Start the wheel running again
  */
-int wheel_start (struct timer_wheel *wheel);
+int wheel_start(struct timer_wheel *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);
+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);
+int wheel_remove_item(struct timer_wheel *wheel, void *item);
 
 #endif