SPROF(1)

NAME
sprof - read and display shared object profiling data

SYNOPSIS
sprof [option]... shared-object-path [profile-data-path]

DESCRIPTION
The sprof command displays a profiling summary for the shared object (shared library) 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 sprof will attempt to deduce it using the soname of the shared object, looking for a file with the name <soname>.profile in the current directory.

OPTIONS
The following command-line options specify the profile output to be produced:

-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.

-p, --flat-profile
    Generate a flat profile of all of the functions in the monitored object, with counts and ticks.

-q, --graph
    Generate a call graph.

If none of the above options is specified, then the default behavior is to display a flat profile and a call graph.

The following additional command-line options are available:

-?, --help
    Display a summary of command-line options and arguments and exit.

--usage
    Display a short usage message and exit.

-V, --version
    Display the program version and exit.

CONFORMING TO
The sprof command is a GNU extension, not present in POSIX.1.

EXAMPLES
The following example demonstrates the use of sprof. The example consists of a main program that calls two functions in a shared object. First, the code of the main program:

    $ cat prog.c
    #include <stdlib.h>
    void x1(void);
    void x2(void);
    int
    main(int argc, char *argv[])
    {
        x1();
        x2();
        exit(EXIT_SUCCESS);
    }

The functions x1() and x2() are defined in the following source file that is used to construct the shared object:

    $ cat libdemo.c
    #include <unistd.h>
    void
    consumeCpu1(int lim)
    {
        for (int j = 0; j < lim; j++)
    	getppid();
    }
    void
    x1(void) {
        for (int j = 0; j < 100; j++)
    	consumeCpu1(200000);
    }
    void
    consumeCpu2(int lim)
    {
        for (int j = 0; j < lim; j++)
    	getppid();
    }
    void
    x2(void)
    {
        for (int j = 0; j < 1000; j++)
    	consumeCpu2(10000);
    }

Now we construct the shared object with the real name libdemo.so.1.0.1, and the soname libdemo.so.1:

    $ cc -g -fPIC -shared -Wl,-soname,libdemo.so.1 \
            -o libdemo.so.1.0.1 libdemo.c

Then we construct symbolic links for the library soname and the library linker name:

    $ ln -sf libdemo.so.1.0.1 libdemo.so.1
    $ ln -sf libdemo.so.1 libdemo.so

Next, we compile the main program, linking it against the shared object, and then list the dynamic dependencies of the program:

    $ cc -g -o prog prog.c -L. -ldemo
    $ ldd prog
    	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)

In order to get profiling information for the shared object, we define the environment variable LD_PROFILE with the soname of the library:

    $ export LD_PROFILE=libdemo.so.1

We then define the environment variable 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:

    $ export LD_PROFILE_OUTPUT=$(pwd)/prof_data
    $ mkdir -p $LD_PROFILE_OUTPUT

LD_PROFILE causes profiling output to be appended to the output file if it already exists, so we ensure that there is no preexisting profiling data:

    $ rm -f $LD_PROFILE_OUTPUT/$LD_PROFILE.profile

We then run the program to produce the profiling output, which is written to a file in the directory specified in LD_PROFILE_OUTPUT:

    $ LD_LIBRARY_PATH=. ./prog
    $ ls prof_data
    libdemo.so.1.profile

We then use the sprof -p option to generate a flat profile with counts and ticks:

    $ sprof -p libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile
    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

The sprof -q option generates a call graph:

    $ sprof -q libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile
    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]
    -----------------------------------------------

Above and below, the "<UNKNOWN>" strings represent identifiers that are outside of the profiled object (in this example, these are instances of main()).

The sprof -c option generates a list of call pairs and the number of their occurrences:

    $ sprof -c libdemo.so.1 $LD_PROFILE_OUTPUT/libdemo.so.1.profile
    <UNKNOWN>                  x1                                 1
    x1                         consumeCpu1                      100
    <UNKNOWN>                  x2                                 1
    x2                         consumeCpu2                     1000

SEE ALSO
gprof(1), ldd(1), ld.so(8)

COLOPHON
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