Add mmtk_worker_count to GC.config

Author: peterzhu2118

gc/mmtk/mmtk.c

@@ -630,8 +630,11 @@ rb_gc_impl_stress_get(void *objspace_ptr)
 VALUE
 rb_gc_impl_config_get(void *objspace_ptr)
 {
-    // TODO
-    return rb_hash_new();
+    VALUE hash = rb_hash_new();
+
+    rb_hash_aset(hash, ID2SYM(rb_intern_const("mmtk_worker_count")), RB_ULONG2NUM(mmtk_worker_count()));
+
+    return hash;
 }
 
 void

gc/mmtk/mmtk.h

@@ -145,6 +145,8 @@ MMTk_Address mmtk_starting_heap_address(void);
 
 MMTk_Address mmtk_last_heap_address(void);
 
+size_t mmtk_worker_count(void);
+
 bool mmtk_is_mmtk_object(MMTk_Address addr);
 
-#endif  /* MMTK_H */
+#endif /* MMTK_H */

gc/mmtk/src/api.rs

@@ -328,6 +328,11 @@ pub extern "C" fn mmtk_last_heap_address() -> Address {
     memory_manager::last_heap_address()
 }
 
+#[no_mangle]
+pub extern "C" fn mmtk_worker_count() -> usize {
+    memory_manager::num_of_workers(mmtk())
+}
+
 // =============== Miscellaneous ===============
 
 #[no_mangle]

test/mmtk/test_configuration.rb

@@ -2,6 +2,16 @@
 require_relative "helper"
 module MMTk
   class TestConfiguration < TestCase
+    def test_MMTK_THREADS
+      assert_separately([{ "MMTK_THREADS" => "5" }], <<~RUBY)
+        assert_equal(5, GC.config[:mmtk_worker_count])
+      RUBY
+
+      assert_separately([{ "MMTK_THREADS" => "1" }], <<~RUBY)
+        assert_equal(1, GC.config[:mmtk_worker_count])
+      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(