Re: igc, macOS avoiding signals

[Pip Cet via "Emacs development discussions." <emacs-devel@gnu.org>]

"Eli Zaretskii" <eliz@gnu.org> writes:

> Ah, okay.  I note that if we'd block signals when calling MPS and
> unblock on exit, then these delays couldn't have happened, AFAIU.

We can't do so for SIGSEGV calling into MPS, so this wouldn't fix all
cases.  Blocking signals around mps_alloc slows down (make-list 1000000
nil) by a factor of about 5 (on current GNU/Linux; possibly
significantly more on other operating systems).

But, yes, if we're willing to give up on unmodified MPS, blocking
signals in the slow path only might work.  We'd need to check
finalizable objects, though, because we need to call into MPS for every
finalizable object.  That's a problem this approach shares with the
allocation thread approach, by the way.  In both cases, registering
objects for finalization doesn't need to happen at allocation time: if
we save a reference to the object somewhere MPS sees it, the objects
won't be collected, so they won't be finalized.

Pip