A file descriptor data structure is configured as a hierarchy of tables. File descriptors are stored as entries in tables that are at the bottom of the hierarchy. When a request to add a file descriptor is received and there are no more entries remaining in the file descriptor tables, the file descriptor data structure is extended by obtaining a lock on a variable containing a maximum number of file descriptors, adding the file descriptor to a new file descriptor table, updating entries in existing upper level tables of the hierarchy so that they point to the new file descriptor table, updating the variable containing the maximum number of file descriptors, and releasing the lock.