MapKit - Trace User Location on Map Without Massive CPU Usage

I'm trying to trace the user's location with a line as they move on a MKMapView. The issue is that I'm currently trying to trace the user's location with a polyline, but when the user's location is updated I'm forced to redraw the line due to a new point being added to it. This hogs massive amounts of cpu resources, as the max cpu usage I experienced was around 200%. How should I draw a path behind the user without using a large portion of the available cpu resources? Below is my code:

var coordinates: [CLLocationCoordinate2D] = [] {
    didSet{
            let polyine = MKPolyline(coordinates: coordinates, count: coordinates.count)
            mapView.removeOverlays(mapView.overlays)
            mapView.add(polyine)
    }
}

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    coordinates.append(locations[0].coordinate)
}

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    let renderer = MKPolylineRenderer(overlay: overlay)

    renderer.strokeColor = UIColor.blue
    renderer.lineWidth = 5.0

    return renderer
}

You shouldn't do:

var coordinates: [CLLocationCoordinate2D] = [] {
    didSet{
        let polyine = MKPolyline(coordinates: coordinates, count: coordinates.count)
        mapView.removeOverlays(mapView.overlays)
        mapView.add(polyine)
    }
}

Because they put a lot of strain on CPU. For example, How about the following code:

var coordinates: [CLLocationCoordinate2D] = [] {
    didSet{
        guard coordinates.count > 1 else {
            return
        }
        let count = coordinates.count
        let start = coordinates[count-1]
        let end = coordinates[count-2]
        let polyine = MKPolyline(coordinates: [start, end], count: 2)
        mapView.add(polyine)
    }
}