Check the option before aggregating live bytes data. Panic if the option is enabled on malloc space.

src/policy/marksweepspace/malloc_ms/global.rs

@@ -274,6 +274,11 @@ impl<VM: VMBinding> MallocSpace<VM> {
     }
 
     pub fn new(args: crate::policy::space::PlanCreateSpaceArgs<VM>) -> Self {
+        if *args.options.count_live_bytes_in_gc {
+            // The implementation of counting live bytes needs a SpaceDescriptor which we do not have for MallocSpace.
+            // Besides we cannot meaningfully measure the live bytes vs total pages for MallocSpace.
+            panic!("count_live_bytes_in_gc is not supported by MallocSpace");
+        }
         MallocSpace {
             phantom: PhantomData,
             active_bytes: AtomicUsize::new(0),

src/scheduler/gc_work.rs

@@ -154,12 +154,14 @@ impl<C: GCWorkContext + 'static> GCWork<C::VM> for Release<C> {
             debug_assert!(result.is_ok());
         }
 
-        let live_bytes = mmtk
-            .scheduler
-            .worker_group
-            .get_and_clear_worker_live_bytes();
-        *mmtk.state.live_bytes_in_last_gc.borrow_mut() =
-            mmtk.aggregate_live_bytes_in_last_gc(live_bytes);
+        if *mmtk.get_options().count_live_bytes_in_gc {
+            let live_bytes = mmtk
+                .scheduler
+                .worker_group
+                .get_and_clear_worker_live_bytes();
+            *mmtk.state.live_bytes_in_last_gc.borrow_mut() =
+                mmtk.aggregate_live_bytes_in_last_gc(live_bytes);
+        }
     }
 }