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

Introducing Ftrace

The kernel function tracer, Ftrace, evolved from work done by Steven Rostedt, and many others, as they were tracking down the causes of high latency. Ftrace appeared in Linux 2.6.27 and has been actively developed since then. There are a number of documents describing kernel tracing in the kernel source in Documentation/trace.

Ftrace consists of a number of tracers that can log various types of activity in the kernel. Here, I am going to talk about the function and function_graph tracers, and about the event tracepoints. In Chapter 14, Real-time Programming, I will revisit Ftrace and use it to show real-time latencies.

The function tracer instruments each kernel function so that calls can be recorded and timestamped. As a matter of interest, it compiles the kernel with the -pg switch to inject the instrumentation, but there the resemblance to gprof ends. The function_graph tracer goes further and records both the entry and exit of functions so that it can create a call graph...