diff --git a/README.md b/README.md
index 28ac4335..581cc638 100644
--- a/README.md
+++ b/README.md
@@ -47,13 +47,20 @@ ninja
 ./FunGame <args>
 gprof ./FunGame gmon.out | gprof2dot | dot -Tsvg -o output.svg
 ```
-Don't know how to turn this off though
-
+To turn off
 ```sh
 rm -rf build # or
 cmake --fresh
 ```
 
+gprof doesn't work with multi-threading. For that we can use perf.
+
+```sh
+perf record -ag ./FunGame Start # or any other commands
+perf script report flamegraph # this will ask to download something
+firefox flamegraph.html
+```
+
 ## Formatting
 
 POSIX shells only
diff --git a/src/util/mesh.hpp b/src/util/mesh.hpp
index 33c7e534..339e3cd9 100644
--- a/src/util/mesh.hpp
+++ b/src/util/mesh.hpp
@@ -151,7 +151,7 @@ class Mesh {
 template <voxel_utility::VoxelLike T>
 std::optional<std::vector<Vertex>>
 analyze_voxel_interface(
-    T voxel_object, VoxelOffset position, VoxelOffset major_direction,
+    const T& voxel_object, VoxelOffset position, VoxelOffset major_direction,
     VoxelOffset minor_direction_1, VoxelOffset minor_direction_2
 ) {
     VoxelColorId voxel_a = voxel_object.get_voxel_color_id(position);
@@ -279,7 +279,7 @@ for dimension (x,y,z direction)
  */
 template <voxel_utility::VoxelLike T>
 Mesh
-ambient_occlusion_mesher(T voxel_object) {
+ambient_occlusion_mesher(const T& voxel_object) {
     std::vector<uint16_t> indicies;
     std::vector<VoxelOffset> indexed_vertices;
     std::vector<MatColorId> indexed_colors;
diff --git a/src/util/voxel.hpp b/src/util/voxel.hpp
index f3f1d327..86dafd49 100644
--- a/src/util/voxel.hpp
+++ b/src/util/voxel.hpp
@@ -158,7 +158,7 @@ class VoxelObject : VoxelBase {
      * @return VoxelSize length in x, y, z
      */
     [[nodiscard]] inline VoxelSize
-    get_size() noexcept {
+    get_size() const noexcept {
         return size_;
     }
 };
diff --git a/src/world/terrain/chunk.hpp b/src/world/terrain/chunk.hpp
index 4c6d51a4..d056ae2f 100644
--- a/src/world/terrain/chunk.hpp
+++ b/src/world/terrain/chunk.hpp
@@ -256,7 +256,7 @@ class ChunkData : public voxel_utility::VoxelBase {
      * @return VoxelSize vector of Chunk::SIZE
      */
     [[nodiscard]] inline VoxelSize
-    get_size() {
+    get_size() const {
         return {Chunk::SIZE, Chunk::SIZE, Chunk::SIZE};
     }