prof(1) UNIX System V(Enhanced Programming Utilities) prof(1)
NAME
prof - display profile data
SYNOPSIS
prof [-t | c | a | n] [-o | x] [-g | l] [-z] [-h] [-s] [-m mdata] -V
[prog]
DESCRIPTION
The prof command interprets a profile file produced by the monitor
function. The symbol table in the object file prog (a.out by default) is
read and correlated with a profile file (mon.out by default). For each
external text symbol the percentage of time spent executing between the
address of that symbol and the address of the next is printed, together
with the number of times that function was called and the average number
of milliseconds per call.
The mutually exclusive options -t, -c, -a, and -n determine the type of
sorting of the output lines:
-t Sort by decreasing percentage of total time (default).
-c Sort by decreasing number of calls.
-a Sort by increasing symbol address.
-n Sort lexically by symbol name.
The mutually exclusive options -o and -x specify the printing of the
address of each symbol monitored:
-o Print each symbol address (in octal) along with the symbol name.
-x Print each symbol address (in hexadecimal) along with the symbol
name.
The mutually exclusive options -g and -l control the type of symbols to
be reported. The -l option must be used with care; it applies the time
spent in a static function to the preceding (in memory) global function,
instead of giving the static function a separate entry in the report. If
all static functions are properly located (see example below), this
feature can be very useful. If not, the resulting report may be
misleading.
Assume that A and B are global functions and only A calls static function
S. If S is located immediately after A in the source code (that is, if S
is properly located), then, with the -l option, the amount of time spent
in A can easily be determined, including the time spent in S. If,
however, both A and B call S, then, if the -l option is used, the report
will be misleading; the time spent during B's call to S will be
attributed to A, making it appear as if more time had been spent in A
than really had. In this case, function S cannot be properly located.
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prof(1) UNIX System V(Enhanced Programming Utilities) prof(1)
-g Include static (non-global) functions.
-l Do not include static (non-global) functions (default).
The following options may be used in any combination:
-z Include all symbols in the profile range, even if associated with
zero number of calls and zero time.
-h Suppress the heading normally printed on the report. (This is
useful if the report is to be processed further.)
-s Print a summary of several of the monitoring parameters and
statistics on the standard error output.
-m mdata
Use file mdata instead of mon.out as the input profile file.
-V Print prof version information on the standard error output.
A program creates a profile file if it has been link edited with the -p
option of cc. This option to the cc command arranges for calls to
monitor at the beginning and end of execution. It is the call to monitor
at the end of execution that causes the system to write a profile file.
The number of calls to a function is tallied if the -p option was used
when the file containing the function was compiled.
The name of the file created by a profiled program is controlled by the
environmental variable PROFDIR. If PROFDIR is not set, mon.out is
produced in the directory current when the program terminates. If
PROFDIR=string, string/pid.progname is produced, where progname consists
of argv[0] with any path prefix removed, and pid is the process ID of the
program. If PROFDIR is set, but null, no profiling output are produced.
A single function may be split into subfunctions for profiling by means
of the MARK macro [see prof(5)].
FILES
mon.out default profile file
a.out default namelist (object) file
SEE ALSO
cc(1), lprof(1), exit(2), profil(2), monitor(3C), prof(5)
The ``lprof'' chapter in the Programmer's Guide: ANSI C and Programming
Support Tools
NOTES
The times reported in successive identical runs may show variances
because of varying cache-hit ratios that result from sharing the cache
with other processes. Even if a program seems to be the only one using
the machine, hidden background or asynchronous processes may blur the
data. In rare cases, the clock ticks initiating recording of the program
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prof(1) UNIX System V(Enhanced Programming Utilities) prof(1)
counter may ``beat'' with loops in a program, grossly distorting
measurements. Call counts are always recorded precisely, however.
Only programs that call exit or return from main are guaranteed to
produce a profile file, unless a final call to monitor is explicitly
coded.
The times for static functions are attributed to the preceding external
text symbol if the -g option is not used. However, the call counts for
the preceding function are still correct; that is, the static function
call counts are not added to the call counts of the external function.
If more than one of the options -t, -c, -a, and -n is specified, the last
option specified is used and the user is warned.
Profiling may be used with dynamically linked executables, but care must
be applied. Currently, shared objects cannot be profiled with prof.
Thus, when a profiled, dynamically linked program is executed, only the
``main'' portion of the image is sampled. This means that all time spent
outside of the ``main'' object, that is, time spent in a shared object,
will not be included in the profile summary; the total time reported for
the program may be less than the total time used by the program.
Because the time spent in a shared object cannot be accounted for, the
use of shared objects should be minimized whenever a program is profiled
with prof. If possible, the program should be linked statically before
being profiled.
Consider an extreme case. A profiled program dynamically linked with the
shared C library spends 100 units of time in some libc routine, say,
malloc. Suppose malloc is called only from routine B and B consumes only
1 unit of time. Suppose further that routine A consumes 10 units of
time, more than any other routine in the ``main'' (profiled) portion of
the image. In this case, prof will conclude that most of the time is
being spent in A and almost no time is being spent in B. From this it
will be almost impossible to tell that the greatest improvement can be
made by looking at routine B and not routine A. The value of the
profiler in this case is severely degraded; the solution is to use
archives as much as possible for profiling.
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