This avoids keeping tree entries around, and free's them as it traverses
the list. This avoids building up a huge memory footprint just for these
small but very common allocations.
Note how the minor fault numbers - which ends up being how many pages we
needed to map - go down from 42934 (167 MB) to 26718 (104 MB). That is:
Before:
42934 minor pagefaults
After:
26718 minor pagefaults
This is all in _addition_ to the previous fixes. It used to be
~48,000 pagefaults.
That's still a honking big memory footprint, but it's about half of what
it was just a day or two ago (and this is the object list for a pretty big
update - almost 60,000 objects. Smaller updates need less memory).
Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Junio C Hamano <junkio@cox.net>