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Date: Thu, 14 Mar 2002 12:14:56 +0100
From: Andi Kleen <ak@suse.de>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>, davidm@hpl.hp.com, linux-kernel@vger.kernel.org,
        torvalds@transmeta.com, rth@twiddle.net
Subject: Re: [PATCH] 2.5.1-pre5: per-cpu areas
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On Thu, Mar 14, 2002 at 10:09:52PM +1100, Rusty Russell wrote:
> Sorry, I think one macro to get the address, one to get the contents
> is a *horrible* interface.  per_cpu() and per_cpu_ptr() or something?


It is not pretty, but I have no choice. See include/asm-x86_64/pda.h on what I 
have currently. Supporting the address in the same macro would 
double to overhead of accesing it. 

> I think you'll find that per_cpu_ptr would be fairly common, so we're
> forced into a bad interface for little gain.  You might be better off
> using another method to implement per-cpu areas.

Nope, the segment register has to stay for other reasons, and it would
be a shame to not use it for cpu data too.

I don't see it as that bad. Is it really that difficult to write _ptr
if you want the address? You can also write _noptr or _direct or whatever
if you don't want the address if you prefer that, but I want to keep
the option to do direct access even for generic code. 


-Andi