Create a benchmark to profile GC performance issue

Author: maximecb

benchmarks/gc_many_objs.psh

@@ -0,0 +1,23 @@
+class Node
+{
+    init(self, val, next)
+    {
+        self.val = val;
+        self.next = next;
+    }
+}
+
+let var list = nil;
+let num_nodes = 1_000_000;
+
+// Grow the list, which will cause multiple GC cycles
+for (let var i = 0; i < num_nodes; ++i)
+{
+    list = Node(1, list);
+}
+
+// Trigger multiple GC cycles in a loop
+for (let var i = 0; i < 10_000; ++i)
+{
+    ByteArray.with_size(100_000);
+}

src/alloc.rs

@@ -55,6 +55,7 @@ impl Alloc
     /// This is primarily used to test the GC
     pub fn shrink_to(&mut self, new_size: usize)
     {
+        assert!(new_size <= self.mem_size);
         assert!(self.next_idx <= new_size);
         self.mem_size = new_size;
 

src/host.rs

@@ -426,6 +426,10 @@ fn vm_shrink_heap(actor: &mut Actor, new_size: Value) -> Result<Value, String>
 {
     let new_size = unwrap_usize!(new_size);
 
+    if new_size > actor.alloc.mem_size() {
+        return Err("requested heap size is larger than the current heap size".into());
+    }
+
     if actor.alloc.bytes_used() > new_size {
         return Err("requested heap size is smaller than bytes currently allocated".into());
     }