Add mmtk_heap_min to GC.config

Author: peterzhu2118

gc/mmtk/mmtk.c

@@ -635,6 +635,8 @@ rb_gc_impl_config_get(void *objspace_ptr)
     rb_hash_aset(hash, ID2SYM(rb_intern_const("mmtk_worker_count")), RB_ULONG2NUM(mmtk_worker_count()));
     rb_hash_aset(hash, ID2SYM(rb_intern_const("mmtk_plan")), rb_str_new_cstr((const char *)mmtk_plan()));
     rb_hash_aset(hash, ID2SYM(rb_intern_const("mmtk_heap_mode")), rb_str_new_cstr((const char *)mmtk_heap_mode()));
+    size_t heap_min = mmtk_heap_min();
+    if (heap_min > 0) rb_hash_aset(hash, ID2SYM(rb_intern_const("mmtk_heap_min")), RB_ULONG2NUM(heap_min));
 
     return hash;
 }

gc/mmtk/mmtk.h

@@ -151,6 +151,8 @@ const uint8_t *mmtk_plan(void);
 
 const uint8_t *mmtk_heap_mode(void);
 
+size_t mmtk_heap_min(void);
+
 bool mmtk_is_mmtk_object(MMTk_Address addr);
 
 #endif  /* MMTK_H */

gc/mmtk/src/api.rs

@@ -359,6 +359,15 @@ pub extern "C" fn mmtk_heap_mode() -> *const u8 {
     }
 }
 
+#[no_mangle]
+pub extern "C" fn mmtk_heap_min() -> usize {
+    match *crate::BINDING.get().unwrap().mmtk.get_options().gc_trigger {
+        GCTriggerSelector::FixedHeapSize(_) => 0,
+        GCTriggerSelector::DynamicHeapSize(min_size, _) => min_size,
+        _ => panic!("Unknown heap mode")
+    }
+}
+
 // =============== Miscellaneous ===============
 
 #[no_mangle]

test/mmtk/test_configuration.rb

@@ -28,6 +28,17 @@ def test_MMTK_THREADS
       end
     end
 
+    def test_MMTK_HEAP_MIN
+      # TODO: uncomment this test when the infinite loop is fixed
+      # assert_separately([{ "MMTK_HEAP_MODE" => "dynamic", "MMTK_HEAP_MIN" => "1" }], <<~RUBY)
+      #   assert_equal(1, GC.config[:mmtk_heap_min])
+      # RUBY
+
+      assert_separately([{ "MMTK_HEAP_MODE" => "dynamic", "MMTK_HEAP_MIN" => "10MiB", "MMTK_HEAP_MAX" => "1GiB" }], <<~RUBY)
+        assert_equal(10 * 1024 * 1024, GC.config[:mmtk_heap_min])
+      RUBY
+    end
+
     %w(MMTK_THREADS MMTK_HEAP_MIN MMTK_HEAP_MAX MMTK_HEAP_MODE MMTK_PLAN).each do |var|
       define_method(:"test_invalid_#{var}") do
         exit_code = assert_in_out_err(