[POWERPC] convert string i/o operations to C

Segher Boessenkool segher at kernel.crashing.org
Wed Sep 20 05:10:34 EST 2006

> For a generic "powerpc" kernel it can be understood, but when you
> consider that on 970/POWER4 and above they use lwsync instead of sync

lwsync (sync 1) doesn't (architecturally) do anything to order MMIO
accesses, so you're misunderstanding something.

> (google for them and see the mailing list posts :), just to breathe  
> back
> some performance in spinlocks and so on, surely this can be  
> rejigged so
> that processors don't do more work than necessary..? Even a noop takes
> time doesn't it?

No-ops don't matter for performance, compared to the cost of the I/O
itself.  It would help to avoid heavier-than-necessary synchronisation
instructions if not needed on some certain CPU (or on non-SMP kernels,


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