PHP extension memory is big than PHP classes of memory

Question

ZEND_METHOD(test, __construct) {
    zval *var_items;

#ifdef FAST_ZPP
    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a", &var_items) == FAILURE) {
        return;
    }
#else
    ZEND_PARSE_PARAMETERS_START(1, 1)
        Z_PARAM_ARRAY(&var_items)
    ZEND_PARSE_PARAMETERS_END();
#endif

    zend_update_property(Z_OBJCE_P(getThis()), getThis(), ZEND_STRL("items"), var_items TSRMLS_CC);
}

The above is an extension class;

But, I using memory_get_usage output memory size,found size is 40000+ byte,this is very big;

This Extension class memory

How can I reduce?