Bug #9687: Make a cap for malloc_limit adjustment

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: 2.2.0
• ruby -v: 2.2
• Backport: 2.0.0: DONTNEED, 2.1: DONE

[ko1 (Koichi Sasada)]

The blog post [Ruby Garbage Collection: Still Not Ready for Production] (http://www.omniref.com/blog/blog/2014/03/27/ruby-garbage-collection-still-not-ready-for-production/) pointed out that the following code consumes all of memory:

while true
  "a" * (1024 ** 2)
end

This is because `malloc_limit' grows and grows infinitely.

The following patch will solve this issue.

Index: gc.c
===================================================================
--- gc.c	(revision 45433)
+++ gc.c	(working copy)
@@ -2890,7 +2890,7 @@ gc_before_sweep(rb_objspace_t *objspace)
 	    malloc_limit = (size_t)(inc * gc_params.malloc_limit_growth_factor);
 	    if (gc_params.malloc_limit_max > 0 && /* ignore max-check if 0 */
 		malloc_limit > gc_params.malloc_limit_max) {
-		malloc_limit = inc;
+		malloc_limit = gc_params.malloc_limit_max;
 	    }
 	}
 	else {

Maybe this patch should be applied for 2.1.x series.

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r45468.

---

• gc.c (gc_before_sweep): cap malloc_limit' to gc_params.malloc_limit_max. It can grow and grow with such case: loop{"a" * (1024 ** 2)}'
  [Bug #9687]
  This issue is pointed by Tim Robertson.
  http://www.omniref.com/blog/blog/2014/03/27/ruby-garbage-collection-still-not-ready-for-production/

[ko1 (Koichi Sasada)]

• Status changed from Closed to Open
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 2.0.0: UNKNOWN, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Open to Closed
• Backport changed from 2.0.0: UNKNOWN, 2.1: REQUIRED to 2.0.0: REQUIRED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED to 2.0.0: DONTNEED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: DONTNEED, 2.1: REQUIRED to 2.0.0: DONTNEED, 2.1: DONE

r45468 was backported into ruby_2_1 branch at r45817.