Re: [Lse-tech] Recalculate trigger in MQ1

[Andi K. <ak...@su...>]

On Thu, Mar 08, 2001 at 09:47:11AM -0500, Hubertus Franke wrote:
> 
> 
> Ahhh, the segment register trick. We did that in the
> K42-OS as well. That ofcourse would be a much cheaper
> way of doing it. Are these kind of special purpose
> registers available across all platforms ?

The most generic way to access a PDA is current->pdapointer that is updated 
in schedule().  This can be hidden in a macro and improved by architecture.
Accessing it this way isn't that costly actually, especially because it can
be done in pure C and therefore CSEd by the compiler.

If you mean using segment registers (different CS) for doing text 
replication, then I'm not sure if it is such a good idea. The CPUs tend 
to drop into all kinds of slow paths when the segment base is not zero.
[on x86-64 it wouldn't work btw, because segment bases are ignored there]

Or did you have something else in mind?


-Andi