The case of running the server with --repair causing spurious warnings of ClientCursor::yield appearing in the logs was resolved in
SERVER-4726. The same warnings appear when using db.runCommand(
) from the shell (or it's helper db.repairDatabase()).
While the warnings are informational only, and the repairDatabase appears to be working correctly, they do cause excessive log size. Even rotated logs of this message could be filled with mostly useless information for a large enough database.