public function getSwapUsed()
    {
        if (count($this->_swapDevices) > 0) {
            $used = 0;
            foreach ($this->_swapDevices as $dev) {
                $used += $dev->getUsed();
            }

            return $used;
        } else {
            return null;
        }
    }
public function getSwapUsed()
    {
        if (count($this->_swapDevices) > 0) {
            $used = 0;
            foreach ($this->_swapDevices as $dev) {
                $used += $dev->getUsed();
            }

            return $used;
        } else {
            return null;
        }
    }
public function getSwapUsed ( ) { if ( count ( $ this -> _swapDevices ) > 0 ) { $ used = 0 ; foreach ( $ this -> _swapDevices as $ dev ) { $ used += $ dev -> getUsed ( ) ; } return $ used ; } else { return null ; } }
Returns total used swap space

@see System::_swapDevices
@see DiskDevice::getUsed()

@return Integer
Returns total used swap space