GNU gprof Profiler Yu Kai Hong Department of Mathematics National Taiwan University July 19, 2008 GNU gprof 1/22.

GNU gprof Profiler

Yu Kai Hong

Department of MathematicsNational Taiwan University

July 19, 2008

GNU gprof 1/22

Two types of time profilers

Built-in UNIX time profiler

- Unix C shell

- Others

GNU gprof time profiler

GNU gprof 2/22


The simplest one.

Does not increase extra time cost.

Does not provide subroutine relative graph.

Does not have to recompile source code.

GNU gprof 3/22


Unix C shell

14.918u: elapsed user time

0.016s: elapsed system time

0:15.61: total elapsed time

95.5%: percent of total CPU usage

0+0k: shared/non-shared memory

0+0io: times for performing input/output

[ykhong@vangogh home]$ time ./test

14.918u 0.016s 0:15.61 95.5% 0+0k 0+0io 0pf+0w

GNU gprof 4/22


Others

real 0m15.456s: total elapsed time

user 0m14.990s: user elapsed time

sys 0m0.015s: system elapsed time

[ykhong@vangogh home]$ time ./test

real 0m15.456s

user 0m14.990s

sys 0m0.015s

GNU gprof 5/22


Detail time statistics for each subroutine.

Create relative graph for all subroutines.

Analysis the program bottleneck.

Increase about 30% extra time cost.

GNU gprof 6/22


Recompile the original source code

-pg: This option affects both compiling and linking.

Add additional commands into source code when

compiling code in order to trace all subroutines.

Add essential initial settings and statistical processes

when linking the objects.

gcc –pg SourceCode –o ExecutableFile

[ykhong@vangogh home]$ gcc –pg test2.c –o test2

GNU gprof 7/22


Convert produced profile data into text file

- ListOfOptions can be omitted.

- ExecuteFile can be omitted when the file name is a.out.

- StatFiles can be omitted when the file name is gmon.out.

gprof ListOfOptions ExecuteFile StatFiles > OutputFile

[ykhong@vangogh home]$ gprof –b test2 gmon.out > output.txt

GNU gprof 8/22


List of Options

-b: omit the table or data illustration on OutputFile.

-e(E) SRName: exclude the subroutine SRName from the table

(and exclude its elapsed time).

-f(F) SRName: only display the subroutine SRName on the

table (and its elapsed time).

GNU gprof 9/22


List of Options

-s: combine more than one StatFile into single one with

default file name gmon.sum.

-Z: only display all subroutines table which are unused

on the program.

GNU gprof 10/22


Example Program

subroutine relative graph

GNU gprof 11/22


Example Program

[ykhong@vangogh home]$ gcc –pg test.c –o test

[ykhong@vangogh home]$ ./test

[ykhong@vangogh home]$ gprof –b test gmon.out > output

[ykhong@vangogh home]$ more output

GNU gprof 2/22


Example Program Each sample counts as 0.01 seconds.

% cumulative self self total

time seconds seconds calls s/call s/call name

71.90 30.17 30.17 1 30.17 30.17 C3

19.42 38.32 8.15 2 4.07 4.07 B2

7.99 41.67 3.35 1 3.35 3.35 C2

0.00 41.67 0.00 1 0.00 37.60 A

0.00 41.67 0.00 1 0.00 33.52 B1

0.00 41.67 0.00 1 0.00 0.00 C1

0.00 41.67 0.00 1 0.00 4.07 D

GNU gprof 13/22


Example Program

% time: the percent of self seconds from total program

elapsed time.

cumulative seconds: the seconds cumulate from self seconds.

self seconds: total elapsed time called by its parents, not

including its children’s elapsed time.

equal to (self s/call)*(calls)

GNU gprof 14/22


Example Program

calls: total number for each subroutine called by its parents.

self s/call: elapsed time for each time called by its parents,

not including its children’s elapsed time.

total s/call: total elapsed time called by its parents,

including its children’s elapsed time.

name: subroutine name.

GNU gprof 15/22


Example Program

Call graph

index %time self children called name

<spontaneous>

[1] 100.0 0.00 41.67 main[1]

0.00 37.60 1/1 A[2]

0.00 4.07 1/1 D[6]

------------------------------------------------------------------

0.00 37.60 1/1 main[1]

[2] 90.2 0.00 37.60 1 A[2]

0.00 33.52 1/1 B1[3]

4.07 0.00 1/2 B2[5]

------------------------------------------------------------------

GNU gprof 16/22


Example Program 0.00 33.52 1/1 A[2]

[3] 80.4 0.00 33.52 1 B1[3]

30.17 0.00 1/1 C3[4]

3.35 0.00 1/1 C2[7]

0.00 0.00 1/1 C1[8]

------------------------------------------------------------------

30.17 0.00 1/1 B1[3]

[4] 72.4 30.17 0.00 1 C3[4]

------------------------------------------------------------------

4.07 0.00 1/2 A[2]

4.07 0.00 1/2 D[6]

[5] 19.6 8.15 0.00 2 B2[5]

------------------------------------------------------------------

GNU gprof 17/22


Example Program

0.00 4.07 1/1 main[1]

[6] 9.8 0.00 4.07 1 D[6]

4.07 0.00 1/2 B2[5]

------------------------------------------------------------------

3.35 0.00 1/1 B1[3]

[7] 8.0 3.35 0.00 1 C2[7]

------------------------------------------------------------------

0.00 0.00 1/1 B1[3]

[8] 0.0 0.00 0.00 1 C1[8]

------------------------------------------------------------------

GNU gprof 18/22

Example Program

[ ] index value for each subroutine


[2]A [8]C1 [6]D

[3]B1 [7]C2

[5]B2 [4]C3

GNU gprof 19/22

Example Program See the second part.

A on the left-most means the relation is viewed for A. B1 and B2 are below of A means A is the parent of B1 and B2 (A calls B1 and B2), main is above of A means A is the child of main (A called by main).


name

<spontaneous>

main[1]

A[2]

D[6]

--------------------

main[1]

A[2]

B1[3]

B2[5]

GNU gprof 20/22

Example Program

See the second part.

1/2 means subroutine B2 is called by

its parents total two times and A calls

it only one time.

1 means subroutine A have only one

parent.


called name

<spontaneous>

main[1]

1/1 A[2]

1/1 D[6]

--------------------

1/1 main[1]

1 A[2]

1/1 B1[3]

1/2 B2[5]

GNU gprof 21/22

Example Program

See the second part

It is viewed for subroutine A. The elapsed time of A’s children is 37.60 seconds and B1’s children is 33.52 seconds.

Especially, B2’s children is 0 second

since B2 doesn’t have any child.


children name

<spontaneous>

41.67 main[1]

37.60 A[2]

4.07 D[6]

--------------------

37.60 main[1]

37.60 A[2]

33.52 B1[3]

0.00 B2[5]

GNU gprof 22/22

GNU gprof Profiler Yu Kai Hong Department of Mathematics National Taiwan University July 19, 2008 GNU gprof 1/22.

Documents

s gnu gprof

output gnu gprof

w gnu gprof

d gnu gprof

time statistics

elapsed user time

elapsed system time

c o test2 gnu gprof