Book Image

Mastering Embedded Linux Programming

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming

By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (22 chapters)
Mastering Embedded Linux Programming
About the Author
About the Reviewers


The idea of swapping is to reserve some storage where the kernel can place pages of memory that are not mapped to a file, so that it can free up the memory for other uses. It increases the effective size of physical memory by the size of the swap file. It is not a panacea: there is a cost to copying pages to and from a swap file which becomes apparent on a system that has too little real memory for the workload it is carrying and begins disk thrashing.

Swap is seldom used on embedded devices because it does not work well with flash storage where constant writing would wear it out quickly. However, you may want to consider swapping to compressed RAM (zram).

Swap to compressed memory (zram)

The zram driver creates RAM-based block devices named /dev/zram0, /dev/zram1, and so on. Pages written to these devices are compressed before being stored. With compression ratios in the range of 30% to 50%, you can expect an overall increase in free memory of about 10%, at the expense of more processing...