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SPROF(1) Linux User Manual 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.

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

SEE ALSO

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

COLOPHON

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2017-09-15 Linux