At some point in the future, barrier() will be universally regarded as
a hammer too big for most purposes. Whether or not removing it now
You can't just remove it, it is needed in some places; you want to
replace it in most places with a more fine-grained "compiler barrier",
I presume?
constitutes premature optimization is arguable, but I think we should
allow such optimization to happen (or not happen) in
architecture-dependent code, and provide a consistent API that doesn't
require the use of such things in arch-independent code where it might
turn into a totally superfluous performance killer depending on what
hardware it gets compiled for.
Explicit barrier()s won't be too hard to replace -- but what to do
about the implicit barrier()s in rmb() etc. etc. -- *those* will be
hard to get rid of, if only because it is hard enough to teach driver
authors about how to use those primitives *already*. It is far from
clear what a good interface like that would look like, anyway.
Probably we should first start experimenting with a forget()-style
micro-barrier (but please, find a better name), and see if a nice
usage pattern shows up that can be turned into an API.
Segher
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