Re: igc, macOS avoiding signals

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

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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.


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From 0aa8b2f483da11bfd6a6397c56182b5877cb779e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gerd=20M=C3=B6llmann?= <gerd@gnu.org>
Date: Mon, 30 Dec 2024 13:41:40 +0100
Subject: [PATCH] Make balancing buffer intervals optional

* src/igc.c (buffer_step): Balance intervals only if
igc__balance_intervals is true.
(syms_of_igc): New DEFVAR_BOOL for igc__balance_intervals.
---
 src/igc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/igc.c b/src/igc.c
index 39158b38f05..964723ce315 100644
--- a/src/igc.c
+++ b/src/igc.c
@@ -3697,7 +3697,8 @@ buffer_step (struct igc_buffer_it *it)
       buffer_it_next (it);
       struct buffer *b = XBUFFER (buf);
       compact_buffer (b);
-      b->text->intervals = balance_intervals (b->text->intervals);
+      if (igc__balance_intervals)
+	b->text->intervals = balance_intervals (b->text->intervals);
       return true;
     }
   return false;
@@ -5100,4 +5101,8 @@ syms_of_igc (void)
 don't do something when idle.  Negative values and values that are not numbers
 are handled as if they were the default value.  */);
   Vigc_step_interval = make_fixnum (0);
+
+  DEFVAR_BOOL ("igc--balance-intervals", igc__balance_intervals,
+     doc: /* Whether to balance buffer intervals when idle.  */);
+  igc__balance_intervals = false;
 }
-- 
2.47.1