Re: [RFC PATCH 1/4] powerpc 2.6.16-rt17: to build on powerpc w/ RT


Well, I've been wanting to look at your stuff and possibly do the
conversion for some time, provided we don't lose performances ... Our
current implementation is very optimized to avoid even memory barriers
in most cases and I doubt we'll be able to be as fine tuned using your
generic code, thus it's a tradeoff decision that we have to do. But
then, I need to look into the details before doing any final
statement :)

Ok, although do let me know if you see places where the generic code
could use any of the optimizations used in powerpc.

Difficult... but maybe. One of the main idea is that the 3 values used
for "calibration" (pre-mult offset, multiplier and post-mult offset) are
in a structure. There is an array of 2 of these and a pointer to the
"current" one. When changing those values, we update the "other" one,
wmb, then flip the pointer. The readers can then mostly be barrier-less
since there is a natural data dependency on the pointer.

Ben.


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