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2019-03-06

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Linux kernel and C library user-space interface documentation

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

This page is part of release 5.00 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

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