Subject: bug#19776: 25.0.50; HTML rendering is very slow

From: Lars Ingebrigtsen <[email-masked]>
Date: Sun, 24 Oct 2021 21:42:24 +0200

Eli Zaretskii <[email-masked]> writes:

> When the timer expires, it delivers a signal, but the signal handler
> only sets a flag.  The flag is checked when we call maybe_quit, which
> calls do_pending_atimers.  So a Lisp program that hogs the CPU, and
> never calls any function that calls maybe_quit, will indeed block
> atimers.  However, this is rare for real-life Lisp programs, because
> several core primitives call maybe_quit from time to time.

The use case here was for CPU-hogging Lisp code, though, like
`shr-insert-document'.  And it doesn't seem to hit any maybe_quits in
this very synthetic test:

(with-delayed-message 0.5 "Yes"
  (dotimes (i 1000000)
    (with-temp-buffer
      (shr-insert-document
       '(html nil
	      (body nil
		    (table nil
			   (tr nil
			       (td nil "Here's a line ")
			       (td nil "Here's a line ")))))))))
      
Could `with-delayed-message' set a flag that would call maybe_quit more
often, somehow?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no