XMPI_Buoy(3) on Linux
The text 652946c6a7f7, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy) shipped it. The page shows this text now.
LAM/MPI-specific function to drop a buoy in the XMPI trace stream.