Methods and apparatus for peer-to-peer data transfers in a computing environment provide configurable control over the number of outstanding read requests by one peer device to another. A requesting peer device includes a control register that stores a high-watermark value associated with requests to a target peer device. Each time a read request to the target peer device is generated, the number of such requests already outstanding is compared to the high-water mark. The request is blocked if the number of outstanding requests exceeds the high-water mark and remains blocked until such time as the number of outstanding requests no longer exceeds the high-water mark. Different high-water marks can be associated with different combinations of requesting and target devices.