sprof - Online in the Cloud

PROGRAM:

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:

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

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