erts: Tweak vheap resizing

erts/emulator/beam/erl_gc.c

@@ -2861,8 +2861,7 @@ shrink_new_heap(Process *p, Uint new_sz, Eterm *objv, int nobj)
 }
 
 static Uint64
-do_next_vheap_size(Uint64 vheap, Uint64 vheap_sz) {
-
+next_vheap_size(Process* p, Uint64 vheap, Uint64 vheap_sz) {
     /*                grow
      *
      * vheap_sz ======================
@@ -2876,35 +2875,31 @@ do_next_vheap_size(Uint64 vheap, Uint64 vheap_sz) {
      * vheap ~ - 25% shrink
      *
      *          ----------------------
+     *
+     * In most benchmarks we see the best performance when growing quickly and
+     * shrinking slowly, so the factors have been chosen accordingly (1.618 is
+     * the golden ratio).
      */
+    static const double growth_factor = 1.618 * 2, shrink_factor = 1.618;
 
-    if ((Uint64) vheap/3 > (Uint64) (vheap_sz/4)) {
-	Uint64 new_vheap_sz = vheap_sz;
+    ASSERT(p->min_vheap_size <= vheap_sz);
 
-	while((Uint64) vheap/3 > (Uint64) (vheap_sz/4)) {
-	    /* the golden ratio = 1.618 */
-	    new_vheap_sz = (Uint64) vheap_sz * 1.618;
-	    if (new_vheap_sz < vheap_sz ) {
-	        return vheap_sz;
-	    }
-	    vheap_sz = new_vheap_sz;
-	}
-
-	return vheap_sz;
+    if (vheap < (vheap_sz / 4)) {
+        return MAX(p->min_vheap_size, (Uint64)(vheap_sz / shrink_factor));
     }
 
-    if (vheap < (Uint64) (vheap_sz/4)) {
-	return (vheap_sz >> 1);
-    }
+    while ((vheap / 3) > (vheap_sz / 4)) {
+        Uint64 new_vheap_sz = vheap_sz * growth_factor;
 
-    return vheap_sz;
+        if (new_vheap_sz < vheap_sz) {
+            return vheap_sz;
+        }
 
-}
+        ASSERT(p->min_vheap_size <= new_vheap_sz);
+        vheap_sz = new_vheap_sz;
+    }
 
-static Uint64
-next_vheap_size(Process* p, Uint64 vheap, Uint64 vheap_sz) {
-    Uint64 new_vheap_sz = do_next_vheap_size(vheap, vheap_sz);
-    return new_vheap_sz < p->min_vheap_size ? p->min_vheap_size : new_vheap_sz;
+    return vheap_sz;
 }
 
 static ERTS_INLINE void