Could you please diagnose my bottleneck?

[[Unknown]]

Is your phone a Nexus 5? That configuration sounds familar.

The Nexus 5 (and possibly other phones) has a firmware bug that limits it to 58/60 fps. This means in games that attempt to run 60 fps, you will need to enable frameskip. This isn't the 17 fps issue, but may help explain other issues.

It's worth noting: PPSSPP tends to be bottlenecked by GPU, or importantly by GPU drivers, more often than other emulators. And based on frameskip, I actually think you are not CPU bottlenecked.

The reason is simple: PPSSPP never skips CPU emulation. Frameskip only skips drawing. If increasing frameskip makes PPSSPP run faster, then you're dealing with something rendering related.

There are lots of things that can impact it as noted - but what game is this, specifically? Another thing to consider is that some PSP games use tricky rendering techniques (you might be surprised the lengths to which some games go to attain outlines around objects, for example), and it could be that this particular scene is doing something that is just slow on modern devices.

There are many rendering techniques which were used on the PSP - a device launched in 2004 - that hardware vendors stopped supporting, because there were better techniques that could be made even faster. But this means those old techniques are now very slow on modern hardware - just no modern game would actually use them.

If your laptop is using an Intel GPU, you may also be better off switching to the Direct3D 11 backend, which may perform better.

-[Unknown]