The present disclosure provides a system for monitoring I/O traffic. The system includes a memory storing information, a device, and a translation lookaside buffer (TLB). The device is configured to send a request for accessing information from the memory. The TLB includes a counter register file having counter registers, and entries having corresponding counter ID fields. The TLB is configured to receive a source identifier of the device and a virtual address associated with the request from the device, select an entry of the entries using the source identifier and the virtual address, select a counter register from the counter registers in accordance with information stored in the counter ID field of the selected entry, and update a value of the selected counter register in accordance with data transferred in association with the request.