Messages in this thread | | | Date | Mon, 13 Aug 2007 02:44:13 -0400 | From | Chris Snook <> | Subject | Re: [PATCH 6/24] make atomic_read() behave consistently on frv |
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David Howells wrote: > Chris Snook <csnook@redhat.com> 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.
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