Method setProductLinks is very slow

I am looping trough 50.000 products. Most with linked items. But it takes forever. It can only handle 1-3 products/second? Is their a faster way than this?

ProductLinkInterfaceFactory $productLink,
ProductRepositoryInterface $productRepository,


*Loop*

$linkData = [];
$productLink = $this->productLink->create();
$productLink->setSku($SKU)
    ->setLinkedProductSku($item)
    ->setPosition($key)
    ->setLinkType('crosssell');
$linkData[] = $productLink;

$productLink = $this->productLink->create();
$productLink->setSku($SKU)
    ->setLinkedProductSku($item)
    ->setPosition($key)
    ->setLinkType('upsell');
$linkData[] = $productLink;


$product = $this->productRepository->get($SKU);
$product->setProductLinks($linkData);
$product->save();