From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: emacs-devel@gnu.org
Subject: Re: [Emacs-diffs] trunk r113437: New unwind-protect flavors to better type-check C callbacks.
Date: Wed, 24 Jul 2013 10:08:39 -0400 [thread overview]
Message-ID: <jwvhafkqciy.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <51EF80E6.9020300@cs.ucla.edu> (Paul Eggert's message of "Wed, 24 Jul 2013 08:23:18 +0100")
> Yes, but the old code had the same problem: make_save_pointer (P)
> created an object that could not be safely used if P's storage was
> freed at the C level.
Oh, that's right.
> Certainly any such performance degradation should be swamped by the
> other performance improvements inherent to the change, as there's no
> longer a need to invoke make_save_pointer, so there's no need to
> create and then garbage-collect an object for each of these
> record_unwind_protect calls: that's such a win that it should be well
> worth possibly losing one branch-predict miss.
I'm not sure about "well worth" because AFAIK these make_save_pointer
calls were only in non-performance-sensitive areas, whereas unbind_to is
used all the time. But I agree that the overall impact is probably
small enough.
Stefan
prev parent reply other threads:[~2013-07-24 14:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <E1UzCuc-0001NQ-T1@vcs.savannah.gnu.org>
2013-07-22 4:13 ` [Emacs-diffs] trunk r113437: New unwind-protect flavors to better type-check C callbacks Stefan Monnier
2013-07-23 9:00 ` Paul Eggert
2013-07-23 13:21 ` Stefan Monnier
2013-07-24 7:23 ` Paul Eggert
2013-07-24 14:08 ` Stefan Monnier [this message]
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