how to expand the pcie rx completion buffer size?

As the documetion says, it is critical to monitor the available RX completion buffer entries to prevent overflow by excessive Non-Posted requests. However, the current RX completion buffer in our IP core has limited capacity - providing only 1,444 credits for Completion Data (CplD), which translates to approximately 1.4μs of buffer time at 500MHz clock frequency with a 512-bit data width. This constraint significantly impacts our ability to maintain optimal outstanding request performance. Could you suggest potential methods to increase the throughput of Non-Posted requests within the current system constraints?