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Optimizing Linux® Performance: A Hands-On Guide to Linux® Performance ToolsBy
Table of Contents
| Index
The first comprehensive, expert guide for end-to-end Linux
application optimization
Learn to choose the right toolsand use them together to
solve real problems in real production environmentsSuperior application performance is more crucial than
everand in today''s complex production environments, it''s
tougher to ensure, too. If you use Linux, you have extraordinary
advantages: complete source code access, plus an exceptional array
of optimization tools. But the tools are scattered across the
Internet. Many are poorly documented. And few experts know how to
use them together to solve real problems. Now, one of those experts
has written the definitive Linux tuning primer for every
professional: Optimizing Linux® Performance.Renowned Linux benchmarking specialist Phillip Ezolt introduces
each of today''s most important Linux optimization tools, showing
how they fit into a proven methodology for perfecting overall
application performance. Using realistic examples, Ezolt shows
developers how to pinpoint exact lines of source code that are
impacting performance. He teaches sysadmins and application
developers how to rapidly drill down to specific bottlenecks, so
they can implement solutions more quickly. You''ll discover how
to:
Identify bottlenecks even if you''re not familiar with the
underlying system
Find and choose the right performance tools for any
problem
Recognize the meaning of the events you''re measuring
Optimize system CPU, user CPU, memory, network I/O, and disk
I/Oand understand their interrelationships
Fix CPU-bound, latency-sensitive, and I/O-bound applications,
through case studies you can easily adapt to your own
environmentInstall and use oprofile, the advanced systemwide profiler for
Linux systemsIf you''re new to tuning, Ezolt gives you a clear and practical
introduction to all the principles and strategies you''ll need. If
you''re migrating to Linux, you''ll quickly master Linux equivalents
to the tools and techniques you already know. Whatever your
background or environment, this book can help you improve the
performance of all your Linux applicationsincreasing
business value and user satisfaction at the same time.
9.7. Optimizing Disk I/O Usage
When you determine that disk I/O is a problem, it can be helpful to determine which application is causing the I/O.Figure 9-5 shows the steps we take to determine the cause of disk I/O usage.
Figure 9-5.
9.7.1. Is the System Stressing a Particular Disk?
Run iostat in the extended statistic mode and look for partitions that have an average wait (await) greater than zero. await is the average number of milliseconds that requests are waiting to be filled. The higher this number, the more the disk is overloaded. You can confirm this overload by looking at the amount of read and write traffic on a disk and determining whether it is close to the maximum amount that the drive can handle.If many files are accessed on a single drive, it may be possible to increase performance by spreading out these files to multiple disks. However, it is first necessary to determine what files are being accessed.Proceed to Section 9.7.2.
9.7.2. Which Application Is Accessing the Disk?
As mentioned in the chapter on disk I/O, this is where it can be difficult to determine which process is causing a large amount of I/O, so we must try to work around the lack of tools to do this directly. By running top, you first look for processes that are nonidle. For each of these processes, proceed to Section 9.7.3.
9.7.3. Which Files Are Accessed by the Application?
First, use strace to Section 9.9.
