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Re: get_mmu_context()

To: linux-mips@fnet.fr
Subject: Re: get_mmu_context()
From: Harald Koerfgen <harald.koerfgen@netcologne.de>
Date: Sun, 18 Oct 1998 21:53:18 +0200 (MEST)
Cc: linux@engr.sgi.com, Vladimir Roganov <roganov@niisi.msk.ru>
In-reply-to: <Pine.SV4.3.91.981016185136.876A-100000@mech.math.msu.su>
Organization: none
Reply-to: "Harald Koerfgen" <harald.koerfgen@netcologne.de>
Sender: harry@franz.no.dom
On 16-Oct-98 Gleb O. Rajko wrote:

> On Thu, 15 Oct 1998 ralf@uni-koblenz.de wrote:
> 
>> 
>> The performance hit will come into the game as soon as one tries to
>> build a generic kernel for both R3000 and R4000.  The R3000 PID and the
>> R4000 ASID mechanism are slightly different and the simple approach
>> to fix that is to use global variables.  Which affects both your version
>> and the current version.
> We are going to provide support for building generic kernels in the near 
> future if somebody who holds r4k will help us and will try our patches 
> on a r4k box. I think the best time to start is when r3k will be synced 
> with the main branch. Perhaps, Harald may answer when it might occur.

Hmmm, I'm not shure about this. If we really want to support generic kernels,
that'll shurely needs some more work than a little patching in get_mmu_context.
Remember, Vladimir, we needed to make changes in extremely performance critical
parts of the kernel which Ralf propably won't like to have for the R4000 case. 
Most
of them are actually compiled conditionally.

To make those changes generic needs either a reasonable amount of hacking or
avoidable code duplication. In fact, if we really don't care about self 
modifying
code we should be able to remove some code duplication, for example in the fpu
stuff.

I'd personally prefer to have a few things sorted out before I check the R3000 
stuff
in. What's common opinion on this?

---
Regards,
Harald

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