Pavel Cahyna wrote:
> On Wed, Apr 26, 2006 at 11:33:44PM -0700, Garrett D'Amore wrote:
>   
>>>  - usr.bin/pmap
>>>
>>>     Ugg.  Maybe the worst of the grovellers.
>>>   
>>>       
>> By its very nature, I suspect pmap is going to "want" to have access to
>> some pretty low level details.  This one might be hard to convert.
>>     
>
> Is it a good idea to convert it? This would mean to invent a stable
> interface between the kernel and userland to examine UVM internal data.
> Later, UVM may change and the interface would not match it anymore. What
> will you do in this case?
>   

Thats the *point* of stable interfaces.  You can change the underlying
stuff, and as long as there is some stable glue, the programs that
depend on it won't break.

Otherwise pmap (or whatever) becomes intrinsically tied to the kernel,
and it is impossible to provide the same kind of information without
being so closely tied.  This makes it hard for e.g. 3rd party OEMs to
write programs which work but are not bundled with the kernel.

Stable APIs are a *GOOD* thing.

    -- Garrett
> Pavel
>   


-- 
Garrett D'Amore, Principal Software Engineer
Tadpole Computer / Computing Technologies Division,
General Dynamics C4 Systems
http://www.tadpolecomputer.com/
Phone: 951 325-2134  Fax: 951 325-2191