Gerd Möllmann <gerd.moellmann@gmail.com> writes:

> Pip Cet <pipcet@protonmail.com> writes:
>
>> Speaking of running with a "normal" config: something about my
>> configuration makes buffer_step (the balance_intervals call, in
>> particular) take forever, to the point the mps build becomes unusable.
>> The buffer in question, when I caught it, is an M-x shell buffer of size
>> 8 MB, so I don't understand why it's taking so long.
>>
>> Still investigating, but skipping the buffer_step seems to help.
>
> balance_intervals means text properties. The only candidate I see in
> comint/shell is ANSI escapes. That could be turned on/off with M-x
> ansi-color-for-comint-mode-xy. Only as a workaround, and maybe to check
> if it's that.
>
> What I do in buffer_step in idle time is basically one step of what the
> old GC does in sweep_buffers.
>
> My expectation was that balancing a tree couldn't take long, and that
> this is not called often enough to be a problem if were expensive. Both
> wrong, as usual.
>
> Not calling balance_intervals is, BTW, not a catastrophic problem. if
> one does anything leading to a graft_intervals_into_buffer, w</r hich is
> called in a lot of places in editfns.c and insdel.c, that balances the
> tree. And if not, the tree might become slower for lookup (redisplay),
> but it still works.
>
> <rant> It's BTW well possible that I myself put that balancing into
> sweep_buffers because of redisplay, I seem to remember that. The
> interval tree has always been a source of fun. I hope, some day, some
> kind soul will eradicate it like the GCPROs. </rant>
>
> In any case, what's a solution?
>
> Right now I'm tending to put the balance_intervals in an if so that one
> can turn it on/off with a Lisp variable. Default would be to not to balance,
> because I think the problems with degenerated interval trees in
> redisplay where rare, and I don't remember problems outside of
> redisplay. But that was an awful long time ago, OTOH.
>
> That would give us more time to think about a possible strategy to solve
> this.
>
> WDYT?

Patch for that attached. I'm now running with that.

I tried to look at the history of intervals.c to see too which degree
the intervals tree is behaving better than decades ago (I think Stefan
Monnier said it's better), but I couldn't really determine that. Too
much has changed.