I tried Zed last month but found that it uses high CPU usage even when idle (up to 50% of 1 core of my i7-7500U).

This is even higher CPU usage than my vscode causes.

Sublime does not do that; in fact it has 0% CPU usage when idle:

    sudo strace -fyp "$(pidof sublime_text)"

(Note, you need to either unfocus it so that the caret stops flashing, or switch from fading caret to fixed / non-fading caret, otherwise it necessarily has to do syscalls to draw itself.)

Zed spams syscalls even when its screen is entirely still:

    strace -fyp "$(pidof zed-editor)"

From what I recall they generally avoid caching anything and just try to repaint the whole UI really, really fast on every frame so I think that's the design.

It's like how a video game renders, which is their stated goal from the beginning.

I always thought their stated design goals were a bit... wonky.

Syscall spamming is one of the main reasons why computers get slow when many apps are running.

Good software does not do that; when idle, it should only consume RAM, not CPU.

Aside: Browsers, and Electron, seem to always syscall-spam no matter what, which is probably a key reason why people feel that all Electron apps bog down their computers. When your computer gets faster, the software just does more syscall loops per second, for unchanged misery.

I've found that some of the language servers can really grind up a storm but Zed itself is usually pretty lightweight.