Enable cyclic region allocation in ART's region space only in debug mode.
Cyclic region allocation can create memory fragmentation at the
region level. Don't use it in non-debug (release) mode.
Test: art/test.py
Test: art/test/testrunner/testrunner.py -t 080-oom-fragmentation
Bug: 33795328
Bug: 74064045
Change-Id: I4619923a86018a17888798bdf247c6d616d5b248
diff --git a/runtime/gc/space/region_space.h b/runtime/gc/space/region_space.h
index c200776..5af1dd3 100644
--- a/runtime/gc/space/region_space.h
+++ b/runtime/gc/space/region_space.h
@@ -35,8 +35,10 @@
// will not try to allocate a new region from the beginning of the
// region space, but from the last allocated region. This allocation
// strategy reduces region reuse and should help catch some GC bugs
-// earlier.
-static constexpr bool kCyclicRegionAllocation = true;
+// earlier. However, cyclic region allocation can also create memory
+// fragmentation at the region level (see b/33795328); therefore, we
+// only enable it in debug mode.
+static constexpr bool kCyclicRegionAllocation = kIsDebugBuild;
// A space that consists of equal-sized regions.
class RegionSpace final : public ContinuousMemMapAllocSpace {