diff options
Diffstat (limited to 'docs/src/roundrobin.dox')
-rw-r--r-- | docs/src/roundrobin.dox | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/docs/src/roundrobin.dox b/docs/src/roundrobin.dox new file mode 100644 index 000000000..8158a5c03 --- /dev/null +++ b/docs/src/roundrobin.dox @@ -0,0 +1,50 @@ +/*
+ ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
+
+ This file is part of ChibiOS/RT.
+
+ ChibiOS/RT is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ ChibiOS/RT is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ 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. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @page article_roundrobin Round Robin scheduling explained
+ * Unlike many other RTOSes, ChibiOS/RT supports multiple threads at the
+ * same priority level and schedules them using an <i>aggressive</i>
+ * round-robin strategy.<br>
+ * The strategy is defined as aggressive because any scheduling event
+ * can cause the round-robin threads to rotate.<br>
+ * A round-robin rotation can happen because of the following events:
+ * - The currently executed thread voluntarily invokes the @p chThdYield()
+ * API in order to allow the execution of another thread at the same
+ * priority level, if any.
+ * - The currently executed thread voluntarily goes into a sleep state
+ * (see @ref thread_states), when the thread is waken it goes behind
+ * all the other threads at the same priority level.
+ * - The currently executed thread is preempted by an higher priority
+ * thread, the thread is reinserted in the ready list (see @ref scheduling)
+ * behind all the other threads at the same priority level.
+ * - If the @p CH_TIME_QUANTUM configuration constant is set to a value
+ * greater than zero and if the specified time quantum expired and if
+ * a thread with equal priority is ready then the currently executing
+ * thread is automatically reinserted in the ready list behind all the
+ * other threads at the same priority level.
+ * .
+ * As you can see the @p CH_TIME_QUANTUM setting is really useful only if
+ * there are threads at the same priority level that can run not preempted
+ * for long periods of time and that do not explicitly yield using
+ * @p chThdYield(). Because of this you should consider to set
+ * @p CH_TIME_QUANTUM to zero in your configuration file, this makes the
+ * kernel much faster and smaller and <b>does not</b> forbid the use of
+ * multiple threads at the same priority level.
+ */
|