xref: /freebsd/share/doc/psd/18.gprof/intro.me (revision 97759ccc715c4b365432c16d763c50eecfcb1100)
Copyright (c) 1982, 1993
The Regents of the University of California. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

.sh 1 "Programs to be Profiled" .pp Software research environments normally include many large programs both for production use and for experimental investigation. These programs are typically modular, in accordance with generally accepted principles of good program design. Often they consist of numerous small routines that implement various abstractions. Sometimes such large programs are written by one programmer who has understood the requirements for these abstractions, and has programmed them appropriately. More frequently the program has had multiple authors and has evolved over time, changing the demands placed on the implementation of the abstractions without changing the implementation itself. Finally, the program may be assembled from a library of abstraction implementations unexamined by the programmer. .pp Once a large program is executable, it is often desirable to increase its speed, especially if small portions of the program are found to dominate its execution time. The purpose of the gprof profiling tool is to help the user evaluate alternative implementations of abstractions. We developed this tool in response to our efforts to improve a code generator we were writing [Graham82]. .pp The gprof design takes advantage of the fact that the programs to be measured are large, structured and hierarchical. We provide a profile in which the execution time for a set of routines that implement an abstraction is collected and charged to that abstraction. The profile can be used to compare and assess the costs of various implementations. .pp The profiler can be linked into a program without special planning by the programmer. The overhead for using gprof is low; both in terms of added execution time and in the volume of profiling information recorded.