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

Profiling with top

top is a simple tool that doesn't require any special kernel options or symbol tables. There is a basic version in BusyBox, and a more functional version in the procps package which is available in the Yocto Project and Buildroot. You may also want to consider using htop which is functionally similar to top but has a nicer user interface (some people think).

To begin with, focus on the summary line of top, which is the second line if you are using BusyBox and the third line if using procps top. Here is an example, using BusyBox top:

Mem: 57044K used, 446172K free, 40K shrd, 3352K buff, 34452K cached
CPU:  58% usr   4% sys   0% nic   0% idle  37% io   0% irq   0% sirq
Load average: 0.24 0.06 0.02 2/51 105
  105   104 root     R    27912   6%  61% ffmpeg -i track2.wav

The summary line shows the percentage of time spent running in various states, as shown in this table:






User space programs...