rein in GC during tests by making them run (at most) once per second

this can provide a significant performance boost during testing, by
preventing the GC from running too frequently.

1 files changed, 24 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/testing/garbage_collection.rb b/activesupport/lib/active_support/testing/garbage_collection.rb
index 7bf9fbafa6..23ac745c3e 100644
--- a/activesupport/lib/active_support/testing/garbage_collection.rb
+++ b/activesupport/lib/active_support/testing/garbage_collection.rb
@@ -3,6 +3,9 @@ module ActiveSupport
     module GarbageCollection
       def self.included(base)
         base.teardown :scrub_leftover_instance_variables
+
+        base.setup :begin_gc_deferment
+        base.teardown :reconsider_gc_deferment
       end
 
       private
@@ -14,6 +17,27 @@ module ActiveSupport
           remove_instance_variable(var)
         end
       end
+
+      # Minimum interval, in seconds, at which to run GC. Might be less
+      # frequently than this, if a single test takes longer than this to
+      # run.
+      DEFERRED_GC_THRESHOLD = (ENV['DEFERRED_GC_THRESHOLD'] || 1.0).to_f
+
+      @@last_gc_run = Time.now
+
+      def begin_gc_deferment
+        GC.disable if DEFERRED_GC_THRESHOLD > 0
+      end
+
+      def reconsider_gc_deferment
+        if DEFERRED_GC_THRESHOLD > 0 && Time.now - @@last_gc_run >= DEFERRED_GC_THRESHOLD
+          GC.enable
+          GC.start
+          GC.disable
+
+          @@last_gc_run = Time.now
+        end
+      end
     end
   end
 end