Luke

August 1, 2026, 4:15pm 1

What would produce the most energy efficient binary? Small or fast? I get that fast will try to produce as fewer instructions as possible but those might be consuming more energy (AVX512). I guess a combination of fast and targeting lower CPU specs?

All this might depend more on the CPU than the compiler anyway.

andrewrk August 1, 2026, 5:45pm 2

That is a very interesting question indeed. None of the optimization modes perfectly align with the goal of energy efficiency, even though fast is quite close to it.

I think, in general, it is a reasonable heuristic that fast mode is also efficient mode because usually to be fast is also to be efficient (Power divided by Work); if you are using more power (numerator), you’re also crunching the data faster (denominator). However, there are exceptions as you pointed out.

I suspect that, in the real world, the best way to achieve energy efficiency is to choose a chip designed for such things, and optimize for fast mode, in which case those use cases will perfectly align.

Let’s keep an eye on this use case, however. I could see a world in which this makes sense as an additional optimization mode.

In practice this is a very under-researched area. You probably just have to go and measure it.

Maybe ask the KDE devs, they have some experience with that.