bug#56682: Fix the long lines font locking related slowdowns

[Stefan Monnier]

Gregory Heytings [2022-08-02 21:43:35] wrote:
>> Hmmm was that using the GNU ELPA `json-mode` package?
> No, it's with emacs -Q.

Sorry, I'm not sure how I missed that you said you used `js-mode`.

> Yes, that's correct.  (But did you test each mode with the same 5 MB buffer?

Yup, a 5MB binary file.

> If so, that's perhaps not representative of what happens in reality.)

Indeed, tho it gives a rough idea of how it can change.

> The general idea is that syntax-ppss is currently an order of
> magnitude too slow for "too large" buffers.

And that it can be almost another order of magnitude worse in some major
modes because of `syntax-propertize`.


        Stefan