David Howells wrote:
Chris Snook <[email protected]> wrote:
cpu_relax() contains a barrier, so it should do the right thing. For non-smp
architectures, I'm concerned about interacting with interrupt handlers. Some
drivers do use atomic_* operations.
I'm not sure that actually answers my question. Why not smp_rmb()?
David
I would assume because we want to waste time efficiently even on non-smp
architectures, rather than frying the CPU or draining the battery. Certain
looping execution patterns can cause the CPU to operate above thermal design
power. I have fans on my workstation that only ever come on when running
LINPACK, and that's generally memory bandwidth-bound. Just imagine what happens
when you're executing the same few non-serializing instructions in a tight loop
without ever stalling on memory fetches, or being scheduled out.
If there's another reason, I'd like to hear it too, because I'm just guessing here.
-- Chris
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