Why is SDL_PollEvent so slow?

Question

Ive been programming an emulator as a side project and am at a point now where I am tackling efficiency. Ive managed to get rid of all the slow things that I was doing like lots of SDL_RenderDrawPoint's, but now I'm stuck.

Ive managed to narrow it down to SDL_PollEvent. Ive simplified my main loop and event loop so that they look similar to a simple SDL tutorial. When I comment out the event loop, the emulator runs super fast. Ive also used the visual studio performance profiler to check, and sure enough, SDL_PollEvent is taking up ~94% of the cpu time.

The place where my emulator does all its stuff is in ppuNptr->cycle() which is taking up only 1.48% .

Unfortunately I can't replicate this in another project so I'm at a loss.

Is there something that I should be doing before polling for events?

How else could I debug this?

Currently im on windows 10 with visual studio 2019 and sdl 2.0.10 .

Answer 1

I too ran across this when profiling my emulator. The answer for me was to downgrade the version of SDL2 to 2.0.8.

I was running SDL2 version 2.0.12 and I took keltar's suggestion in the comments, and downgraded to 2.0.8 and I was no longer having the issue with the SDL_PollEvent causing slow performance. This fixed the issue for me as I no longer having low FPS issues with my emulator.

I will see if this issue has been reported in the bug ticketing system and report it if not to the SDL2 as this issue starts occurring from version 2.0.9.