Converting Valgrind callgrinds to SVG format

post, Feb 28, 2024, on Mitja Felicijan's blog

Lately I have been doing a lot of systems programming and profiling is the name of the game when it comes to developing good software.

I found Valgrind indispensable for profiling and getting callgraphs.

Most of the time there are better alternatives that SVG to drill intro the callgraphs but if you need to put put a callgraph on a webpage or maybe send it to somebody that does not have all of the necessary software to view these things then SVG is the perfect format for this.

Theses are couple of amazing applications to view callgraphs that get exported by Valgrind:

This is how Kcachekrind looks with a callgraph loaded in. Not only that, with Kcachegrind you can also explore assembly produced by the compiler and get much more insight into the profile of your application.

Kcachekrind screenshot

After this point you will need couple of things installed on your system. I will show how you do this on Fedora 39.

# Install valgrind which will do the actual profiling.
sudo dnf install valgrind

# Install Kcachegrind for local visualizing.
sudo dnf install kcachegrind

# Install gprof2dot for conversion from .dot to .svg.
pip install gprof2dot  

Let's make a simple C program and test out profiling and the whole shebang.

#include <stdio.h>

int main() {
  printf("Oh, hi Mark\n");
  return 0;

Then let's compile, convert to dot and then SVG file.

clang hi.c -o c-hi
valgrind --tool=callgrind --dump-instr=yes --collect-jumps=yes ./c-hi
gprof2dot --format=callgrind --colormap=print callgrind.out.546168
cat | dot -Tsvg > out.c.svg

This gives us an SVG file like this.

SVG callgrind for C program

And this also works on other binaries.

Lets give Zig a go.

const std = @import("std");

pub fn main() !void {
  std.debug.print("Oh, hi Mark!\n", .{});

Now repeat the whole compile, convert cycle.

zig build-exe hi.zig --name zig-hi
valgrind --tool=callgrind --dump-instr=yes --collect-jumps=yes ./zig-hi
gprof2dot --format=callgrind --colormap=print callgrind.out.546168
cat | dot -Tsvg > out.zig.svg
SVG callgrind for Zig program

Now, to be fair Kcachegrind is much nicer for local exploration and digging deep into the callgraphs, but the SVG format can still provide valid information for documentation and things of that nature.

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