Linux debugging and performance tuning tips and techniques

Linux Debugging and Performance Tuning

Linux(R) Debugging and Performance Tuning: Tips and Techniques

Steve Best, Prentice Hall PTR, ISBN-13: 978-0131492479

Guide to Linux software debugging & tuning at both kernel and application levels. Using extensive Linux code examples, Steve Best systematically introduces open source tools and best-practice techniques for delivering bug-free, well-tuned code. Topics include:

• bottleneck identification,
• code coverage,
• debuggers: gdb, kgdb, kdb and DDD.
• Memory management,
• /proc kernel data analysis,
• system process monitoring,
• network performance,
• oops bug messages syslog,
• execution traces, including strace, ltrace
• profiling, including gprof and OProfile
• dynamic probes (kprobes),
• User Mode Linux (UML),
• crash dump analysis.

For nearly each topic related to debugging and performance tuning, this book has at least hints on how to start and which tools to use. In nearly any case, this will be enough to get you started and to understand the limitations. You will have to do extra research to understand all details of each tool. The book is not geared towards embedded — the concepts of cross-development / cross-debugging or specific architectures are never mentioned.

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Linux Debugging and Performance Tuning: Tips and Techniques

• Sorry, this book is no longer in print.

About

Features

A unique resource that shows Linux kernel AND Linux application programmers how to write bug-free code that’s optimized for performance.

° Debugging tools and techniques for the Linux kernel itself and Linux applications

° Performance tools and techniques that show how to supercharge the kernel and the applications that run on it.

° Sophisticated profiling techniques that teach programmers how to uncover application bottlenecks

Description

• Copyright 2006
• Dimensions: 7″ x 9-1/4″
• Pages: 456
• Edition: 1st

• Book
• ISBN-10: 0-13-149247-0
• ISBN-13: 978-0-13-149247-9

Learn Linux debugging and optimization—at kernel and application levels—hands-on!

This is the definitive guide to Linux software debugging and performance optimization at both the kernel and application levels. Using extensive Linux code examples, Steve Best systematically introduces open source tools and best-practice techniques for delivering bug-free, well-tuned code.

Drawing on his exceptional experience optimizing Linux systems for IBM, Best covers issues ranging from memory management and I/O to system processes and kernel bug messages. You’ll walk through real debugging sessions, discovering the strategies experts use to debug even the most complex application- and kernel-related problems. You’ll master sophisticated profiling techniques for identifying and resolving bottlenecks more quickly and learn how to capture the right data in the event of trouble. Coverage includes

Debuggers: gdb, kgdb, and KDB

/proc kernel data analysis

System process monitoring

Oops bug messages

Syslog and event logging

Profiling kernel behavior

Crash dump analysis

Linux® Debugging and Performance Tuning will be indispensable for every developer who needs to supercharge the Linux kernel and applications, and for every administrator and support specialist who must resolve Linux reliability or performance issues.

© Copyright Pearson Education. All rights reserved.

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Table of Contents

About the Author.

2. Code Coverage.

3. GNU Debugger (gdb).

4. Memory Management Debugging.

5. System Information (/proc).

7. System Error Messages.

8. Event Logging.

9. Linux Trace Toolkit.

10. oprofile: a Profiler Supported by the Kernel.

11. User-Mode Linux.

12. Dynamic Probes.

13. Kernel-Level Debuggers (kgdb and kdb).

Preface

Introduction

The book includes many sample programs that demonstrate how to use the best profiling and debugging tools available for Linux. All the tools are open-source and continue to be enhanced by the open-source community.

The goal of the book is to provide you with the knowledge and skills you need to understand and solve software problems on Linux servers. It discusses techniques and tools used to capture the correct data using first failure data capture approaches.

This Book’s Audience

Chapter Descriptions

Chapter 1, «Profiling,» discusses methods to measure execution time and real-time performance. Application performance tuning is a complex process that requires correlating pieces of data with source code to locate and analyze performance problems. This chapter shows a sample program that is tuned using a profiler called gprof and a code coverage tool called gcov.

Chapter 2, «Code Coverage,» discusses coverage code that can be used to determine how well your test suites work. One indirect benefit of gcov is that its output can be used to identify which test case provides coverage for which source file. Code coverage during testing is one important measurement of software quality. Like an X-ray machine, gcov peers into your code and reports on its inner workings.

What would debugging be without a debugger? Chapter 3, «GNU Debugger (gdb),» looks at the GNU debugger. You can debug by adding printf statements to a program, but this is clumsy and very time-consuming. A debugger like gdb is a much more efficient debugging tool.

Chapter 4, «Memory Management Debugging,» looks at the APIs for memory management, which, although small, can give rise to a large number of disparate problems. These include reading and using uninitialized memory, reading/writing from memory past or in front of (underrun) the allocated size, reading/writing inappropriate areas on the stack, and memory leaks. This chapter covers four memory management checkers: MEMWATCH, YAMD, Electric Fence, and Valgrind. We’ll review the basics, write some «buggy» code, and then use each of these tools to find the mistakes.

The /proc file system is a special window into the running Linux kernel and is covered in Chapter 5, «System Information (/proc).» The /proc file system provides a wealth of information for the Linux kernel. It offers information about each process to system-wide information about CPU, memory, file systems, interrupts, and partitions. Some of the utilities that use /proc entries to get data from the system include iostat, sar, lsdev, lsusb, lspci, vmstat, and mpstat. Each of these utilities is covered in the chapter.

Chapter 6, «System Tools,» looks at various tools that can be used to pinpoint what is happening to the system and to find which component of the system is having a problem. The ps command is a valuable tool that can be used to report the status of each of the system processes. Three other process tools are covered—pgrep, pstree, and top. The strace command lets you trace system calls. The magic key sequence can provide a back trace for all the processes on the system. The lsof tool can be used to list the open files on the system. Finally, the network debugging tools ifconfig, arp, ethereal, netstat, and tcpdump are covered. They can help solve network-type problems.

Many kernel bugs show themselves as NULL pointer dereferences or other values to pointers that are incorrect. The common result of such a bug is the Oops message. Chapter 7, «System Error Messages,» covers where an Oops message is stored, how to analyze the Oops, and finding the failing line of code.

An important goal of a Linux systems administrator is to ensure that his or her systems are functioning and performing 100 % of the time. Applications producing error messages, file systems not having free space available, network adapter failures, hard drives producing errors, and the kernel producing errors are just a few types of problems that could possibly stop a system, impacting that goal. Chapter 8, «Event Logging,» helps administrators grapple with these issues by describing Syslog and event logging.

Chapter 9, «Linux Trace Toolkit,» shows how an execution trace shows exactly what scheduling decisions are made and how various management tasks are done. It captures how they are handled, how long they take, and to which process the processor has been allocated. The trace facility provides a dynamic way to gather system data. Application I/O latencies can also be identified, as well as the time when a specific application is actually reading from a disk. Certain types of locking issues also can be seen by tracing.

In short, tracing can be used to

• Isolate and understand system problems.
• Observe system and application execution for measuring system performance.
• Permit bottleneck analysis when many processes are interacting and communicating.

The Linux Trace Toolkit (LTT) differs from strace or gprof in that LTT provides a global view of the system, including a view into the kernel.

Chapter 10, «oprofile: a Profiler Supported by the Kernel,» covers the kernel profiler called oprofile. Profilers are software development tools designed to help analyze the performance of applications and the kernel. They can be used to identify sections of code that aren’t performing as expected. They provide measurements of how long a routine takes to execute, how often it is called, where it is called from, and how much time it takes. Profiling is also covered in Chapter 1; one profiler in that chapter is called gprof. Another topic covered in Chapter 10 is ways to minimizing cache misses. Cache misses can be a cause of applications not performing as expected.

User-Mode Linux (UML) is covered in Chapter 11, «User-Mode Linux»; it is a fully functional Linux kernel. It runs its own scheduler and virtual memory (VM) system, relying on the host kernel for hardware support. The benefits of UML from a debugging point of view are that it lets you do kernel development and debugging at the source code level using gdb. The UML technology can be a powerful tool to reduce the time needed to debug a kernel problem and development kernel-level features.

Chapter 12, «Dynamic Probes,» explains dynamic probes (Dprobes), which is a technique for acquiring diagnostic information without custom-building the component. Dynamic probes can also be used as a tracing mechanism for both user and kernel space. It can be used to debug software problems that are encountered in a production environment that can’t be re-created in a test lab environment. Dprobes are particularly useful in production environments where the use of an interactive debugger is either undesirable or unavailable. Dprobes also can be used during the code development phase to cause faults or error injections into code paths that are being tested.

Chapter 13, «Kernel-Level Debuggers (kgdb and kdb),» covers two kernel-level debuggers: kgdb and kdb. kgdb is an extension to gdb that allows the gdb debugger to debug kernel-level code. One key feature of kgdb is that it allows source code-level debugging of kernel-level code. The kdb debugger allows kernel-level debugging but does not provide source-level debugging.

There are multiple ways for Linux to support a crash dump. Chapter 14, «Crash Dump,» covers the different types of crash dumps. It discusses Linux Kernel Crash Dump (LKCD), Netdump, Diskdump, and mcore. Crash dump is designed to meet the needs of end users, support personnel, and systems administrators needing a reliable method of detecting, saving, and examining system problems. There are many benefits of having a bug report and dump of the problem, since the dump provides a significant amount of information about the system’s state at the time of the problem.

Foreword

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Index

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Linux Debugging and Performance Tuning: Tips and Techniques

©2006 | Pearson | Out of print

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Overview

Description

A unique resource that shows Linux kernel AND Linux application programmers how to write bug-free code that’s optimized for performance.

1) Debugging techniques for Linux applications and the kernel

2) Performance tuning techniques for Linux application and the kernel.

3) Sample programs that show how debugging tools can find programming errors.

4) Sample programs that show how profiling tools can show which routines applications spend the most time in.

5) Key features that can be set up in the kernel to capture data once a problem occurs.

Series

This product is part of the following series. Click on a series title to see the full list of products in the series.

Pearson Open Source Software Development Series

Look Inside

Sample chapter is available for download in PDF format.

This material is protected under all copyright laws, as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher.

° Debugging tools and techniques for the Linux kernel itself and Linux applications

° Performance tools and techniques that show how to supercharge the kernel and the applications that run on it.

° Sophisticated profiling techniques that teach programmers how to uncover application bottlenecks

Features

A unique resource that shows Linux kernel AND Linux application programmers how to write bug-free code that’s optimized for performance.

В° Debugging tools and techniques for the Linux kernel itself and Linux applications

В° Performance tools and techniques that show how to supercharge the kernel and the applications that run on it.

В° Sophisticated profiling techniques that teach programmers how to uncover application bottlenecks

Table of Contents

About the Author.

2. Code Coverage.

3. GNU Debugger (gdb).

4. Memory Management Debugging.

5. System Information (/proc).

7. System Error Messages.

8. Event Logging.

9. Linux Trace Toolkit.

10. oprofile: a Profiler Supported by the Kernel.

11. User-Mode Linux.

12. Dynamic Probes.

13. Kernel-Level Debuggers (kgdb and kdb).

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About the Author(s)

Steve Best works in the Linux Technology Center of IBM in Austin, Texas. He is currently working on Linux storage-related products. Steve has led the Journaled File System (JFS) for Linux project. Steve has worked on Linux-related projects since 1999 and has done extensive work in operating system development focusing on file systems, internationalization, and security. Steve is the author of numerous magazine articles, many presentations, and the file system chapters in Performance Tuning Linux Servers (Prentice Hall PTR 2005).

В© Copyright Pearson Education. All rights reserved.

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