Книга: Real-Time Concepts for Embedded Systems
13.1 Introduction
13.1 Introduction
Embedded systems developers commonly implement custom memory-management facilities on top of what the underlying RTOS provides. Understanding memory management is therefore an important aspect of developing for embedded systems.
Knowing the capability of the memory management system can aid application design and help avoid pitfalls. For example, in many existing embedded applications, the dynamic memory allocation routine, malloc, is called often. It can create an undesirable side effect called memory fragmentation. This generic memory allocation routine, depending on its implementation, might impact an application's performance. In addition, it might not support the allocation behavior required by the application.
Many embedded devices (such as PDAs, cell phones, and digital cameras) have a limited number of applications (tasks) that can run in parallel at any given time, but these devices have small amounts of physical memory onboard. Larger embedded devices (such as network routers and web servers) have more physical memory installed, but these embedded systems also tend to operate in a more dynamic environment, therefore making more demands on memory. Regardless of the type of embedded system, the common requirements placed on a memory management system are minimal fragmentation, minimal management overhead, and deterministic allocation time.
This chapter focuses on:
· memory fragmentation and memory compaction,
· an example implementation of the malloc and free functions,
· fixed-size, pool-based memory management,
· blocking vs. non-blocking memory functions, and
· the hardware memory management unit (MMU).
Оглавление книги
- Introduction to Microprocessors and Microcontrollers
- Introduction
- 5.1 Introduction
- Introduction to Serial Devices
- 14.1 Introduction
- Introduction to PHP
- 3.4.1. Introduction to Atomic Transactions
- 11.1. Introduction to BusyBox
- 1.1 Introduction
- 2.5.1. Introduction to Group Communication
- 4.1.1. Introduction to Threads
- 6.1. INTRODUCTION