/* 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 . */ /** * @page article_manage_memory How to manage memory * ChibiOS/RT is a static kernel so you don't need to manage memory at all * if your application doesn't really require it. This doesn't mean that * the OS is unable to manage memory but just that memory management is an * optional part of the whole.
* The OS offers three distinct ways to manage memory, each one with its * weaknesses and strengths: * - Core Memory Manager. See @ref memcore. * - Heap Allocator. See @ref heaps. * - Memory Pools. See @ref pools. * . * The three mechanisms are able to coexist and are well integrated, as example * the heap allocator uses the core memory manager in order to get more * memory blocks, memory pools can optionally do the same thing. * *

The three subsystems

* This is a small comparison table regarding the three subsystems, C-runtime * and static objects are thrown in there for comparison:

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Subsystem * * Free capable * * Constant time * * Safe * * From IRQ * * Notes *
* Static Objects * N/AN/AYESYES * Preferred solution for safety applications. *
* Core Memory Manager * NOYESYESYES * Fast and safe but unable to free allocated memory. *
* Heap Allocator * YESNONONO * Unsafe because fragmentation and not constant time, cannot be used * from IRQ handlers. *
* Memory Pools * YESYESYESYES * Fast and safe but it can handle fixed size objects only, you may have * multiple memory pools however. *
* C-Runtime * YESNONONO * Unsafe because fragmentation, not constant time, cannot be used * from IRQ handlers and not thread safe. The C runtime must also be * modified in order to work with the other allocators. *
*
* When designing a system it is recommended to proceed as follow: * -# Use static objects and initializers whenever possible. * -# Where dynamic allocation is required without have to free the allocated * memory then use the Core Memory Manager allocation APIs. * -# Where dynamic allocation is required evaluate if one or more memory * pools can be used. * -# If all the above points do not satisfy your requirements then use the * heap allocator. * -# Consider the C-runtime allocator only for legacy code. * . */