Re: For the AdaOS folks

["Warren W. Gay VE3WWG" <ve3wwg@NoSpam.cogeco.ca>]

Luke A. Guest wrote:
> On Sun, 02 Jan 2005 22:13:47 -0500, Warren W. Gay VE3WWG wrote:
>>>>>Correct. That's why a protected AmigaOS must support protection domains
>>>>>not only for processes but also for libraries. That's a generalization
>>>>>of the UNIX model. There you have protection domains for each process
>>>>>plus one protection domain for the kernel which is mainly a huge
>>>>>library. In AmigaOS every library would need its own protection domain
>>>>>and context switches must be as lightweight as possible.
>>>
>>>I certainly wouldn't do it like that. On hardware that has an MMU (most
>>>these days), that would result in a very slow system due to the amount of
>>>context switches, this is why the libraries need to be mapped into the
>>>address space of the running app, i.e. shared between applications.
>>
>>There is no argument about the overhead in this case. However, I
>>maintain that if enough people start using operating systems
>>that are implemented this way, they'll finally enhance the
>>hardware to correct this problem. Until then, people may as well
>>continue to say "we can't do it that way". I believe the problem
>>is fixable in hardware.
> 
> Yeah but, what you were saying was that you wanted OSes to use protection
> domains for libraries *as well*, this is the wrong way to go. The
> libraries are (and should be) mapped into an applications address space,
> libraries *should never* have their own address spaces. It is that idea
> which is wrong and would be slow, not the *proper* way to do it.

Oh, no - I don't know where you got that from (perhaps you've mixed me
up with a different poster). Shared libraries have an important
role to play.
--
Warren W. Gay VE3WWG
http://home.cogeco.ca/~ve3wwg