private boolean isDeepUnmodifiable(Map<String,Object> map) {
        for (Object value : map.values())
            if (value instanceof QueryProfile && !((QueryProfile)value).isFrozen()) return false;
        return true; // all other values are primitives
    }
Create a WRITABLE instance with some initial state
container-search/src/main/java/com/yahoo/search/query/profile/CopyOnWriteContent.java