For review: sprof(1) manual page

["Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>]

Hello all,

There is currently no good documentation of glibc's 'sprof'
command, so I wrote the man page below. Comments, error reports,
and suggestions for improvement welcome.

Thanks

Michael


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.TH SPROF 1 2014-06-10 "Linux" "Linux User Manual"
.SH NAME
sprof \- read and display shared object profiling data
.SH SYNOPSIS
.nf
.BR sprof " [OPTION]... SHARED-OBJECT-PATH [PROFILE-DATA-PATH]"
.fi
.SH DESCRIPTION
The
.B sprof
command displays a profiling summary for the
shared object specified as its first command-line argument.
The profiling summary is created using previously generated
profiling data in the (optional) second command-line argument.
If the profiling data pathname is omitted, then
.B sprof
will attempt to deduce it using the soname of the shared object,
looking for a file with the name
.IR <soname>.profile
in the current directory.
.SH OPTIONS
The following command-line options specify the profile output
to be produced:
.TP
.BR \-c ", " \-\-call\-pairs
Print a list of pairs of call paths for the interfaces exported
by the shared object,
along with the number of times each path is used.
.TP
.BR \-p ", " \-\-flat\-profile
Generate a flat profile of all of the functions in the monitored object,
with counts and ticks.
.TP
.BR \-q ", " \-\-graph
Generate a call graph.
.PP
If none of the above options are specified,
then the default behavior is to display a flat profile and a call graph.
.PP
The following additional command-line options are available:
.TP
.BR \-? ", " \-\-help
Display a summary of command-line options and arguments and exit.
.TP
.BR \-\-usage
Display a short usage message and exit.
.TP
.BR \-V ", " \-\-version
Display the program version and exit.
.SH CONFORMING TO
The
.B sprof
command is a GNU extension, not present in POSIX.1.
.SH EXAMPLE
The following example demonstrates the use of
.BR sprof .
The example consists of a main program that calls two functions
in a shared library.
First, the code of the main program:

.in +4n
.nf
$ \fBcat prog.c\fP
#include <stdlib.h>

void x1(void);
void x2(void);

int
main(int argc, char *argv[])
{
    x1();
    x2();
    exit(EXIT_SUCCESS);
}
.fi
.in
.PP
The functions
.IR x1()
and
.IR x2()
are defined in the following source file that is used to
construct the shared library:

.in +4n
.nf
$ \fBcat libdemo.c\fP
#include <unistd.h>

void
consumeCpu1(int lim)
{
    int j;

    for (j = 0; j < lim; j++)
	getppid();
}

void
x1(void) {
    int j;

    for (j = 0; j < 100; j++)
	consumeCpu1(200000);
}

void
consumeCpu2(int lim)
{
    int j;

    for (j = 0; j < lim; j++)
	getppid();
}

void
x2(void)
{
    int j;

    for (j = 0; j < 1000; j++)
	consumeCpu2(10000);
}
.fi
.in
.PP
Now we construct the shared library with the real name
.IR libdemo.so.1.0.1 ,
and the soname
.IR libdemo.so.1 :

.in +4n
.nf
$ \fBcc \-g \-fPIC \-shared \-Wl,\-soname,libdemo.so.1 \e\fP
        \fB\-o libdemo.so.1.0.1 libdemo.c\fP
.fi
.in
.PP
Then we construct symbolic links for the library soname and
the library linker name:

.in +4n
.nf
$ \fBln \-sf libdemo.so.1.0.1 libdemo.so.1\fP
$ \fBln \-sf libdemo.so.1 libdemo.so\fP
.fi
.in
.PP
Next, we compile the main program, linking it against the shared library,
and then list the dynamic dependencies of the program:

.in +4n
.nf
$ \fBcc \-g \-o prog prog.c \-L. \-ldemo\fP
$ \fBldd prog\fP
	linux\-vdso.so.1 =>  (0x00007fff86d66000)
	libdemo.so.1 => not found
	libc.so.6 => /lib64/libc.so.6 (0x00007fd4dc138000)
	/lib64/ld\-linux\-x86\-64.so.2 (0x00007fd4dc51f000)
.fi
.in
.PP
In order to get profiling information for the shared library,
we define the environment variable
.BR LD_PROFILE
with the soname of the library:

.in +4n
.nf
$ \fBexport LD_PROFILE=libdemo.so.1\fP
.fi
.in
.PP
We then define the environment variable
.BR LD_PROFILE_OUTPUT
with the pathname of the directory where profile output should be written,
and create that directory if it does not exist already:

.in +4n
.nf
$ \fBexport LD_PROFILE_OUTPUT=$(pwd)/prof_data\fP
$ \fBmkdir \-p $LD_PROFILE_OUTPUT\fP
.fi
.in
.PP
.B LD_PROFILE
causes profiling output to be
.I appended
to the output file if it already exists,
so we ensure that there is no preexisting profiling data:

.in +4n
.nf
$ \fBrm \-f $LD_PROFILE_OUTPUT/$LD_PROFILE.profile\fP
.fi
.in
.PP
We then run the program to produce the profiling output,
which is written to a file in the directory specified in
.BR LD_PROFILE_OUTPUT :

.in +4n
.nf
$ \fBLD_LIBRARY_PATH=. ./prog\fP
$ \fBls prof_data\fP
libdemo.so.1.profile
.fi
.in
.PP
We then use the
.BR "sprof \-p"
option to generate a flat profile with counts and ticks:

.in +4n
.nf
$ \fBsprof \-p libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile\fP
Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  us/call  us/call  name
 60.00      0.06     0.06      100   600.00           consumeCpu1
 40.00      0.10     0.04     1000    40.00           consumeCpu2
  0.00      0.10     0.00        1     0.00           x1
  0.00      0.10     0.00        1     0.00           x2
.fi
.in
.PP
The
.BR "sprof \-q"
option generates a call graph:

.in +4n
.nf
$ \fBsprof \-q libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile\fP

index % time    self  children    called     name

                0.00    0.00      100/100         x1 [1]
[0]    100.0    0.00    0.00      100         consumeCpu1 [0]
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
                0.00    0.00        1/1           <UNKNOWN>
[1]      0.0    0.00    0.00        1         x1 [1]
                0.00    0.00      100/100         consumeCpu1 [0]
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
                0.00    0.00     1000/1000        x2 [3]
[2]      0.0    0.00    0.00     1000         consumeCpu2 [2]
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
                0.00    0.00        1/1           <UNKNOWN>
[3]      0.0    0.00    0.00        1         x2 [3]
                0.00    0.00     1000/1000        consumeCpu2 [2]
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
.fi
.in
.PP
Above and below, the "<UNKNOWN>" strings represent identifiers that
are outside of the profiled object (in this example, these are instances of
.IR main() ).
.PP
The
.BR "sprof \-c"
option generates a list of call pairs and the number of their occurrences:

.in +4n
.nf
$ \fBsprof \-c libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile\fP
<UNKNOWN>                  x1                                 1
x1                         consumeCpu1                      100
<UNKNOWN>                  x2                                 1
x2                         consumeCpu2                     1000
.fi
.in
.SH SEE ALSO
.BR gprof (1),
.BR ldd (1),
.BR ld.so (8)


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/