On Thu, Sep 04 2025, Gerd Möllmann wrote:

> Helmut Eller <eller.helmut@gmail.com> writes:
[...]
>> What would you think of making mps_arena_step and perhaps buffer_step
>> available from Lisp so that those things can be called from Lisp-level
>> idle timers?
>
> Sounds like a good idea.

Below is a patch that does this.

The idle timer waits 2 seconds, before it calls mps_arena_step.  As
usual, "idle time" is the time since the last command completed, i.e. 2
seconds must pass after a command before the idle timer fires.  (Other
timers or process filters don't reset "idle time"; only new commands
do.)  I think that should avoid the problem that I've seen where
opportunistic GC was started while I was in the middle of typing
something.

The code uses a constant to predict the idle time; maybe one could to
something a bit more clever; not sure if that would be worth the
trouble.

Regarding bug#76505 (or https://github.com/Ravenbrook/mps/issues/305),
I now think that it's safe to call mps_arena_step with multiplier=0:
The expression (availableEnd - now) never overflows because the
invariant now <= intervalEnd <= availableEnd holds.