I've been developing a C++ OpenGL game for the last couple of months.

A few weeks ago I was profiling the game and I noticed that the GPU usage was almost at 100% (with the framerate uncapped). I added a new feature and the GPU usage capped at arround 35% (also with the framerate unlocked).

At first I thought that this was about CPU bottleneck, but the CPU was also around 35% usage.

I was expecting the framerate to lower after that update (and it did, from about 2000 to 600) but I thought that the CPU / GPU usage would still be high.

Having the GPU usage this low makes me think that I should be getting more FPS.

Is this behaviour normal, or did I do something wrong?

  • 5
    \$\begingroup\$ When you check the CPU usage, make sure you check all cores separately. Maybe one of your cores is at 100% while the others are idle. \$\endgroup\$
    – Vaillancourt
    Commented Sep 9, 2021 at 0:02
  • 1
    \$\begingroup\$ There are also other possible resource bottlenecks, like memory access, pcie lanes or file IO which can cause both gpu and cpu to stall. Did you rule those out? \$\endgroup\$
    – Philipp
    Commented Sep 9, 2021 at 8:09
  • \$\begingroup\$ @Vaillancourt , that was it. One of the CPU cores is performing at 95% while the others are lower. Thank you! \$\endgroup\$ Commented Sep 9, 2021 at 13:26
  • \$\begingroup\$ Glad I could help! You're free to write an answer to your own question if you want :) \$\endgroup\$
    – Vaillancourt
    Commented Sep 9, 2021 at 13:38

1 Answer 1


As @Vaillancourt pointed out, even though the CPU wasn't getting high usage percentage, one of it's cores was. I guess it's time to improve the multi-threading of my game!


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