Assuming Jiraiya is starting at base. Mu takes this med-high diff. I don't see why people seem to think barrier could pose a threat to Mu, after all Mu can sense the barrier and fly outside of it while spamming Jinton from long range to kill any summon Jiraiya brings in to this fight. Even if Jiraiya were to enter SM, he will still die. He has decent reflexes but not enough. Pein was able to take his arm easily, Jinton is quite fast and deadly.
As long as Mu keeps flying and spamming Jinton, Jiraiya can't get near him.