How to make the result of callgrind human readable

I'm trying to use valgrind --tool=callgrind to profile my C++ program on Ubuntu. Here is my code:

#include <iostream>
int main()
{
    std::cout<<"hello world"<<std::endl;
    return 0;
}

Compile it: g++ main.cpp -g

valgrind: valgrind --tool=callgrind ./a.out

Then I get a file named callgrind.out.1153.

Then I use the tool gprof2dot and the command dot:

python gprof2dot.py -f callgrind -n10 -s callgrind.out.1153 > valgrind.dot
dot -Tpng valgrind.dot -o valgrind.png

However, this png is like this:

For me this is really hard to read.

So is it possible to make callgrind more human readable? For example, can it show me only the execution time of each function of my code or the execution time of my code line by line?

It's not super user-friendly, but I think this does what the OP wants:

callgrind_annotate --tree=both --inclusive=yes --auto=yes --show-percs=yes callgrind.out.${pid} > tree.${pid}

This creates a text file with two sections. The first section is a summary of profiled functions, sorted by the time spent in each. Example of one function:

 3,090,761,742,907 (22.39%)  < /home/me/proj/src/dir0/file0.cpp:caller0() (79,173,695x) [/home/me/proj/build/reldbg/lib/libzero.so]
   768,380,030,255 ( 5.57%)  < /home/me/proj/src/dir0/file1.cpp:caller1(unsigned int) (19,814,000x) [/home/me/proj/build/reldbg/lib/libzero.so]
 3,861,537,817,283 (27.97%)  *  /home/me/proj/src/dir0/Abc.cpp:Abc::Abc() [/home/me/proj/build/reldbg/lib/libzero.so]
 2,458,035,862,297 (17.80%)  >   /home/me/proj/src/dir1/file2.h:callee0() (99,049,427x) [/home/me/proj/build/reldbg/lib/libone.so]
 1,378,046,252,252 ( 9.98%)  >   /home/me/proj/src/dir0/file3.cpp:callee1() (99,049,427x) [/home/me/proj/build/reldbg/lib/libzero.so]

The profiled function has the asterisk, its callers have less-than, the functions it calls have greater-than.

The second section is annotated source code, with the amount of time allocated on each line. For example:

--------------------------------------------------------------------------------
-- Auto-annotated source: /home/me/proj/src/dir0/file1.cpp
--------------------------------------------------------------------------------
Ir                      

-- line 37 ----------------------------------------
 7,822,093,316 ( 0.06%)          for (uint32 i = 0; i < VEC_SIZE; i++)
             .                   {
21,018,143,872 ( 0.15%)              data[i].reset();
110,822,940,416 ( 0.80%)  => /home/me/proj/src/dir0/abc.cpp:Abc::reset() (1,910,740,352x)
             .                   }