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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.
9.6. Optimizing Memory Usage
Often, it is common that a program that uses a large amount of memory can cause other performance problems to occur, such as cache misses, translation lookaside buffer (TLB) misses, and swapping.Figure 9-4 shows the flowchart of decisions that we will make to figure out how the system memory is being used.
Figure 9-4.
9.6.1. Is the Kernel Memory Usage Increasing?
To track down what is using the system's memory, you first have to determine whether the kernel itself is allocating memory. Run slabtop and see whether the total size of the kernel's memory is increasing. If it is increasing, jump to Section 9.6.2.If the kernel's memory usage is not increasing, it may be a particular process causing the increase. To track down which process is responsible for the increase in memory usage, go to Section 9.6.3.
9.6.2. What Type of Memory Is the Kernel Using?
If the kernel's Section 9.9.
9.6.3. Is a Particular Process's Resident Set Size Increasing?
Next, you can use top or ps to see whether a particular process's resident set size is increasing. It is easiest to add the rss field to the output of top and sort by memory usage. If a particular process is increasingly using more memory, we need to figure out what type of memory it is using. To figure out what type of memory the application is using, go to Section 9.6.6. If no particular process is using more memory, go to Section 9.6.4.
9.6.4. Is Shared Memory Usage Increasing?
Use ipcs to determine whether the amount of shared memory being used is increasing. If it is, go to Section 9.9.
9.6.5. Which Processes Are Using the Shared Memory?
Use ipcs to determine Section 9.9.
9.6.6. What Type of Memory Is the Process Using?
The easiest way to see what types of memory the process is using is to look at its status in the /proc file system. This file, cat /proc/<pid>/status, gives a breakdown of the processs memory usage.If the process has a large and increasing VmStk, this means that the processs stack size is increasing. To analyze why, go to Section 9.6.7.If the process has a large VmExe, that means that the executable size is big. To figure out which functions in the executable contribute to this size, go to Section 9.6.8. If the process has a large VmLib, that means that the process is using either a large number of shared libraries or a few large-sized shared libraries. To figure out which libraries contribute to this size, go to Section 9.6.9. If the process has a large and increasing VmData, this means that the processs data area, or heap, is increasing. To analyze why, go to Section 9.6.10.
9.6.7. What Functions Are Using All of the Stack?
To figure out Section 9.9.
9.6.8. What Functions Have the Biggest Text Size?
If the executable has a sizable amount of memory being used, it may be useful to determine which functions are taking up the greatest amount of space and prune unnecessary functionality. For an executable or library compiled with symbols, it is possible to ask nm to show the size of all the symbols and sort them with the following command:
With the knowledge of the size of each function, it may be possible to reduce their size or remove unnecessary code from the Section 9.9.
nm -S size-sort
9.6.9. How Big Are the Libraries That the Process Uses?
The easiest way Section 9.9.
9.6.10. What Functions Are Allocating Heap Memory?
If your application is Section 9.9.
