Add Book to My BookshelfPurchase This Book Online

Chapter 9 - System Configuration and Resource Limits

UNIX Systems Programming for SVR4
David A. Curry
 Copyright © 1996 O'Reilly & Associates, Inc.

Chapter 9: System Configuration and Resource Limits
Overview
To support a wide variety of applications, ranging from a single-user workstation system to a multi-user timesharing system, the UNIX operating system has always offered the system administrator a number of parameters that can be “tuned” to make the system perform better under specific types of load. Some of these parameters control the behavior of the operating system kernel proper: how many file table entries to allocate, how much memory to allocate for interprocess communication, how many process table slots to use, and so forth. Other parameters control individual processes, such as how many open files a process may have, how much memory it may use, and how large a file it may create, to prevent a single process from consuming the entire system's resources.
In early versions of the UNIX system, almost all of these parameters were defined using constants in system include files. This meant that after changing one of the parameters, every program that used the parameter had to be recompiled. Gradually, particularly as third-party vendors began selling software for the UNIX system, the values of more and more of these parameters could be determined, and sometimes changed, via system calls and library routines. This enabled software to be more portable: if a program could determine at runtime what its limits were, it did not have to be recompiled on each system where those limits were different. POSIX and other UNIX standardization efforts have improved this situation even more, by defining standard interfaces and standard resource names, enabling programs to portably determine almost any limit they may need to know.
In this chapter, we describe the system configuration parameters and the routines available for accessing and modifying them. We also examine the calls available for getting and setting per-process resource limits, and look at the routines available for determining how many system resources a process has used.

Previous SectionNext Section
Books24x7.com, Inc © 2000 –  Feedback