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.

EXAMPLE

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)
{
    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);
}

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: