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SPROF

Section: Linux User Manual (1)
Updated: 2017-09-15
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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

COLOPHON

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