Ran xcp scan -du on a 30TB NFS share, which would approximately have 120million files.
xcp scan took about 6 hours to scan 104million files, but after that for next 10hrs it was in same state but i see continuous "xcp re-opener" and "mod time chnaged, reading anyway" warning/info event in the logs.
im using 1.7 xcp version, attaching the xcp logs for reference.