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

Beginning to profile

When looking at the entire system, a good place to start is with a simple tool like top, which gives you an overview very quickly. It shows you how much memory is being used, which processes are eating CPU cycles, and how this is spread across different cores and time.

If top shows that a single application is using up all the CPU cycles in user space then you can profile that application using perf.

If two or more processes have a high CPU usage, there is probably something that is coupling them together, perhaps data communication. If a lot of cycles are spent in system calls or handling interrupts, then there may be an issue with the kernel configuration or with a device driver. In either case you need to start by taking a profile of the whole system, again using perf.

If you want to find out more about the kernel and the sequencing of events there, you would use Ftrace or LTTng.

There could be other problems that top will not help you with. If you have multi-threaded...