The winger arrived from Wolves for a club record fee last summer.
Allardyce told whufc.com: "Matt has been outstanding. He has the best crossing stats in the Premier League and not in just terms of quantity but the regular quality. So it shows what a valuable player he has been for us this season. It was a massive move for him, because it was a reasonable size fee for him, not a big one. He has to live with that a little bit and find his way in and now he has come to life for me.
"The good thing is that Matt Jarvis gives our players a rest, because when he gets it, he's going to turn and run at opposition defenders. He's going to run to the opposition's box, do his tricks and nine times out of ten he's going to produce a cross. It's a huge, huge asset for us, when you've got a player who can hang onto the ball as long as he can."