Re: [RFC, experimental] save_{excursion,restriction}

[Stefan Monnier]

> It's worth trying to redesign save-restriction and save-excursion to avoid
> allocating Lisp data. I tried some hacks for save-excursion, and it's quite
> surprising: initially, running (while t (scroll-up) (sit-for 0.05)) over
> just loaded xdisp.c with font-lock enabled asks for 600 GCs, and with this
> patch it's just 350.

save-restriction should be fairly rare (and if it's not, that's
something we should fix), but for save-excursion I'm not that surprised.
BTW, could you resend your patch but changing it so the new
save_excursion_save/save_excursion_restore replace the old one directly
in the text, so the patch hunks show what is changed and what
stays unchanged?
Also, you need to mark the `excursions' field during GC.


        Stefan


PS: Another source of slowdown for save-excursion is the unchain_marker call.