GNU bug report logs - #54698
non-recursive GC marking [PATCH]

Previous Next

Full log

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Mattias Engdegård <mattiase <at> acm.org>
To: bug-gnu-emacs <at> gnu.org
Subject: non-recursive GC marking [PATCH]
Date: Sun, 3 Apr 2022 20:40:57 +0200

[Message part 1 (text/plain, inline)]

The GC uses recursion to traverse data structures for marking which imposes a limit to how big (or deeply nested) Lisp data structures can be, and usually results in an immediate Emacs crash without warning when that limit is exceeded.

The attached patch replaces recursion with an explicit stack for most common object types: conses, vectors, records, hash tables, symbols, functions etc. Recursion remains for some less common types (buffers, frames etc) but these are typically not used in quantities to cause a problem.

A side benefit is that GC becomes quite a bit faster as a result. Actual workloads such as byte-compilation are consequently sped up by a small but measurable amount.

The patch is explicitly unfinished in some uninteresting respects to make it easier to read; `process_mark_stack` needs reindenting.

[gc-mark-stack.diff (application/octet-stream, attachment)]

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.