"Dummy" View consuming a lot of CPU

Hello all, 

I am facing a "strange" problem here : my application has a view that shows current locks held by other users : 

Here is the code of the view : 

CREATE VIEW "ORA_LOCKS" ("SID", "SERIAL", "TYPE",

  "USERNAME")

AS

  SELECT

    s.sid,

    serial# serial,

    s.type,

    username

  FROM

    sys.v_$session s,

    sys.v_$locked_object l

  WHERE

    s.sid = l.session_id;

I ran a ADDM report the other day on one of the databases, and I was very surprised that this view is consuming a lot of CPU time as all I'm doing is a SELECT * FROM ORA_LOCKS...