Special casing tasks by interactive credit was helpful for preventing fully
cpu bound tasks from easily rising to interactive status.

However it did not select out tasks that had periods of being fully cpu
bound and then sleeping while waiting on pipes, signals etc.  This led to a
more disproportionate share of cpu time.

Backing this out will no longer special case only fully cpu bound tasks,
and prevents the variable behaviour that occurs at startup before tasks
declare themseleves interactive or not, and speeds up application startup
slightly under certain circumstances.  It does cost in interactivity
slightly as load rises but it is worth it for the fairness gains.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>