I suspect it masks the problem.  Try this out:

set vfs.lfs.pagetrip to something sane, such as ssize/4096/4.  Each
time you decrease it (by powers of two), try untarring pkgsrc (this is
on a multiprocessor machine, since we're talking about locking).  The
last decrement in pagetrip should be ssize/PAGE_SIZE.  Notice how, if
you get deadlocks, etc., they seem to happen more often as you go
lower.  Now, try setting pagetrip to something one or two powers of
two lower than ssize/PAGE_SIZE, such as 64.  Now notice how quickly it
locks!

I suspected this has to do with the lfs writer daemon ltsleeping,
given the time it sleeps is fixed.  Haven't gotten a chance to look at
it more, though.

Any thoughts?

Regards,

--Blair