[Bug 1898] Optional CPU dependent _Per_CPU_Information attributes

[bugzilla-daemon at rtems.org]

https://www.rtems.org/bugzilla/show_bug.cgi?id=1898

--- Comment #5 from Chris Johns <chrisj at rtems.org> 2011-08-21 17:29:35 CDT ---
(In reply to comment #4)
> I think I would prefer to broaden this PR a bit.  
> 
> We use CPU_STRUCTURE_ALIGNMENT for only one structure -- the priority bit maps.
> The Per CPU data is also critical.   
> 
> Maybe we should add "CPU_STRUCTURE_SHORT_DATA" to do what you are suggesting.
> Or CPU_STRUCTURE_FAST_DATA which is the port's way of answering the question:  

I agree with the last one. It describes why rather than a how. How can vary but
why will not.

> "Generically RTEMS knows it has a very few data structures which if access can
> be optimized, then what does the port recommend?"
> 
> I can see using both attributes on both pieces of data for speed.  Per CPU
> should be aligned and in short data if possible.  The priority bit map access
> time impacts the time required for a preemptive thread to block voluntarily.
> 
> What do you think?

Short may not map to a CPU so may not make sense.

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