erts: Reinstate copy_object over-allocation optimization

3 files changed, 22 insertions, 19 deletions

diff --git a/erts/emulator/beam/copy.c b/erts/emulator/beam/copy.c
index 38c40f4e7d..3de2c10203 100644
--- a/erts/emulator/beam/copy.c
+++ b/erts/emulator/beam/copy.c
@@ -40,29 +40,30 @@ static void move_one_frag(Eterm** hpp, ErlHeapFragment*, ErlOffHeap*);
 /*
  *  Copy object "obj" to process p.
  */
-Eterm
-copy_object(Eterm obj, Process* to)
-{
-    Uint size = size_object(obj);
-    Eterm* hp = HAlloc(to, size);
-    Eterm res;
+Eterm copy_object_x(Eterm obj, Process* to, Uint extra) {
+    if (!is_immed(obj)) {
+        Uint size = size_object(obj);
+        Eterm* hp = HAllocX(to, size, extra);
+        Eterm res;
 
 #ifdef USE_VM_PROBES
-    if (DTRACE_ENABLED(copy_object)) {
-        DTRACE_CHARBUF(proc_name, 64);
+        if (DTRACE_ENABLED(copy_object)) {
+            DTRACE_CHARBUF(proc_name, 64);
 
-        erts_snprintf(proc_name, sizeof(DTRACE_CHARBUF_NAME(proc_name)),
-                      "%T", to->common.id);
-        DTRACE2(copy_object, proc_name, size);
-    }
+            erts_snprintf(proc_name, sizeof(DTRACE_CHARBUF_NAME(proc_name)),
+                    "%T", to->common.id);
+            DTRACE2(copy_object, proc_name, size);
+        }
 #endif
-    res = copy_struct(obj, size, &hp, &to->off_heap);
+        res = copy_struct(obj, size, &hp, &to->off_heap);
 #ifdef DEBUG
-    if (eq(obj, res) == 0) {
-	erl_exit(ERTS_ABORT_EXIT, "copy not equal to source\n");
-    }
+        if (eq(obj, res) == 0) {
+            erl_exit(ERTS_ABORT_EXIT, "copy not equal to source\n");
+        }
 #endif
-    return res;
+        return res;
+    }
+    return obj;
 }
 
 /*
diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c
index ae9a853411..8047711e6f 100644
--- a/erts/emulator/beam/erl_db_util.c
+++ b/erts/emulator/beam/erl_db_util.c
@@ -2160,7 +2160,7 @@ restart:
 	    n = *pc++;
 	    ASSERT(is_value(variables[n].term));
 	    ASSERT(!variables[n].proc);
-	    variables[n].term = copy_object(variables[n].term, c_p);
+	    variables[n].term = copy_object_x(variables[n].term, c_p, HEAP_XTRA);
 	    *esp++ = variables[n].term;
 	    #ifdef DEBUG
 	    variables[n].proc = c_p;
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 3559f0cd13..870afb414f 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -954,7 +954,9 @@ __decl_noreturn void __noreturn erl_exit_flush_async(int n, char*, ...);
 void erl_error(char*, va_list);
 
 /* copy.c */
-Eterm copy_object(Eterm, Process*);
+Eterm copy_object_x(Eterm, Process*, Uint);
+#define copy_object(Term, Proc) copy_object_x(Term,Proc,0)
+
 Uint size_object(Eterm);
 Eterm copy_struct(Eterm, Uint, Eterm**, ErlOffHeap*);
 Eterm copy_shallow(Eterm*, Uint, Eterm**, ErlOffHeap*);