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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

By : Chris Simmonds
4.8 (20)
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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

4.8 (20)
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 (16 chapters)
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15
Index

How much memory does my application use?

As with kernel space, the different ways of allocating, mapping and sharing user space memory make it quite difficult to answer this seemingly simple question.

To begin with, you can ask the kernel how much memory it thinks is available, which you can do by using the free command. Here is a typical example of the output:

             total     used     free   shared  buffers   cached
Mem:        509016   504312     4704        0    26456   363860
-/+ buffers/cache:   113996   395020
Swap:            0        0        0

Tip

At first sight, this looks like a system that is almost out of memory with only 4704 KiB free out of 509,016 KiB: less than 1%. However, note that 26,456 KiB is in buffers and a whopping 363,860 KiB is in cache. Linux believes that free memory is wasted memory and so the kernel uses free memory for buffers and caches, in the knowledge that they can be shrunk when the need arises. Removing buffers and cache from the measurement gives...

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