Bernhard Kast wrote:
> Hi!
>
> I am not quite sure, why the servers and the user
> applications run in the same privilege level of
> the cpu.
> Taking a look at the Intel Architecture Manuals,
> I would say it is cheaper (no privilege check,
> no stack switch) for user level processes to
> interact with the servers and/or it is just
> not necessary to have them run in different
> levels.
> Or is it for compability reasons? (I don't think
> so.)
>
> ftp://download.intel.com/design/Pent...s/25366517.pdf
> page 160-162
> from here:
> http://www.intel.com/design/pentium4.../index_new.htm
>
> thx in advance
> Bernhard

So you'd rather have the servers run in kernel-mode?

Miix 3 uses a Microkernel where only a little tiny bit of code runs in
kerel-mode the rest is user-mode.

Microkernel. Say it, biatch.

Hello

I think there is an issue with vocabulary here.
I don't understand what are the "servers" that you mention.
Usually "servers" are either physical or logical entities that answers to
client queries. There are simple servers like HTTP and complex servers like
multimedia servers.
If you mean OS parts as "servers", then you must remenber that Minix is not
a complex OS.
Minix is very reminiscent of Unix on PDP11 architecture without MM. You can
find traces of this by the vocabulary "user mode", "kernel mode", use of
chmem which imply a very simple memory allocation for processes.
At that time you do not use more than one program at a time as a user.
Unix was intended to make time sharing not multi tasking, i.e. process
switch is awkward the process must be copied integrally somewhere else, then
the new process is launched.
Many interprocess means was offered at that time (IPC, pipes, shared
memory). But it was not satisfying developpers.
The main reason is the lack of virtual memory which forbid to share some
code between different processes.
Threads came later with more complex CPU. Many attemps where done in the 80'
BSD, Chorus, Amoeba.
Threads are offered commercially since the beginning of the 90'.
To offer threads you need a CPU with MMU.

Another thing driving the use of complex CPU is the fact that the lowering
prices of hardware enables:
- At end user level: The ability to launch multiple applications
simultaneously and paste and cut data between them making productivity
jumping far ahead.
- At IT staff level the ability to specialize computers in server or client
(workstation) role, to simplify user care and deployment of new applications
lowering TCO.
- The use of more abstracted programming paradigm, COM/Corba, simple Object
languages with garbage collectors like Java, lowering the cost of
developpement, script languages with dynamic and/or weak typing that are
awful to a computer scientist but understandable by a mere human being.

As users and managers waited for communicating processes and/or computers,
complex CPU where produced.
These CPU where able to enable processes to communicate in a (relatively)
secure manner.
Pentium IV is an incredible giant when you compare it to a PDP11.
It's not fair to compare Minix CPU model with a PentiumIV.
Minix is more oriented toward appliances (only one application running
without needing care or administration) and education.

A good description of this all is there:
http://www.prenhall.com/divisions/es...e/right_3.html

One final thing, I am not sure that the OS design culminates with Posix
compliant with internal Coba and (X-)Windows of the infernal duo
Windows/Linux.
In fact I find Linux boring in it's cloning obsession (after Unix, now its
more and more MS Windows-ish).
It remains to see if it have any interest to work at improving OS design
with today's Googlarization of IT.

One good thing that Minix can bring is putting very different research ideas
of this century, like Multimedia Roma OS, on a larger audience.
Other research ideas would be Semantic Web integration at the OS level.
In the past interesting OSes have also been killed by Unix, like Pick OS,
where there was no file system but a huge database. Unfortunately you had to
learn programming and Database to use it. But if you combine a modern
requesting UI with that idea it's quite funny.
Other ideas would be to make tiny OS inside bigger OS to tackle with
unsecure tasks like browsing the Web.
(please don't mention Plan9 or grid computing :-)

Jean-Pierre


"Bernhard Kast" a écrit dans le message de
news:43922fce$0$708$79720d31@newsreader.inode.at.. .
> Hi!
>
> I am not quite sure, why the servers and the user
> applications run in the same privilege level of
> the cpu.
> Taking a look at the Intel Architecture Manuals,
> I would say it is cheaper (no privilege check,
> no stack switch) for user level processes to
> interact with the servers and/or it is just
> not necessary to have them run in different
> levels.
> Or is it for compability reasons? (I don't think
> so.)
>
> ftp://download.intel.com/design/Pent...s/25366517.pdf
> page 160-162
> from here:
> http://www.intel.com/design/pentium4.../index_new.htm
>
> thx in advance
> Bernhard

> So you'd rather have the servers run in kernel-mode?
no, sorry I forgot to mention the following:

protect.h
#define INTR_PRIVILEGE 0 /* kernel and interrupt handlers */
#define TASK_PRIVILEGE 1 /* kernel tasks */
#define USER_PRIVILEGE 3 /* servers and user processes */

to be more exactly, why the servers are not running in
Privilege level 2 (ring 2 for the cpu)?
(I understand, why the server is not running
in privilege level 0 and 1.)

Bernhard


Segin wrote:
> Bernhard Kast wrote:
>
>> Hi!
>>
>> I am not quite sure, why the servers and the user
>> applications run in the same privilege level of
>> the cpu.
>> Taking a look at the Intel Architecture Manuals,
>> I would say it is cheaper (no privilege check,
>> no stack switch) for user level processes to
>> interact with the servers and/or it is just
>> not necessary to have them run in different
>> levels.
>> Or is it for compability reasons? (I don't think
>> so.)
>>
>> ftp://download.intel.com/design/Pent...s/25366517.pdf
>> page 160-162
>> from here:
>> http://www.intel.com/design/pentium4.../index_new.htm
>>
>> thx in advance
>> Bernhard
>
>
> So you'd rather have the servers run in kernel-mode?
>
> Miix 3 uses a Microkernel where only a little tiny bit of code runs in
> kerel-mode the rest is user-mode.
>
> Microkernel. Say it, biatch.

Hi!

eeh, well I think there is some sort of misunderstanding
around here, with servers I meant the "servers in Minix".

http://www.minix3.org/doc/AppendixB....RIVILEGE-05843
#define INTR_PRIVILEGE 0 /* kernel and interrupt handlers */
#define TASK_PRIVILEGE 1 /* kernel tasks */
#define USER_PRIVILEGE 3 /* servers and user processes */

In Minix the filesystem, memory management etc. are called
servers, because the provide a service, well it is a
microkernel.
> If you mean OS parts as "servers", then you must remenber that Minix
> is not a complex OS.
well, sorry I didn't give them the name and from my OS
knowledge it was logically that they are called servers,
therefore I wasn't more specific.

Bernhard


Jean-Pierre Le Rouzic wrote:
> Hello
>
> I think there is an issue with vocabulary here.
> I don't understand what are the "servers" that you mention.
> Usually "servers" are either physical or logical entities that answers to
> client queries. There are simple servers like HTTP and complex servers like
> multimedia servers.
> If you mean OS parts as "servers", then you must remenber that Minix is not
> a complex OS.
> Minix is very reminiscent of Unix on PDP11 architecture without MM. You can
> find traces of this by the vocabulary "user mode", "kernel mode", use of
> chmem which imply a very simple memory allocation for processes.
> At that time you do not use more than one program at a time as a user.
> Unix was intended to make time sharing not multi tasking, i.e. process
> switch is awkward the process must be copied integrally somewhere else, then
> the new process is launched.
> Many interprocess means was offered at that time (IPC, pipes, shared
> memory). But it was not satisfying developpers.
> The main reason is the lack of virtual memory which forbid to share some
> code between different processes.
> Threads came later with more complex CPU. Many attemps where done in the 80'
> BSD, Chorus, Amoeba.
> Threads are offered commercially since the beginning of the 90'.
> To offer threads you need a CPU with MMU.
>
> Another thing driving the use of complex CPU is the fact that the lowering
> prices of hardware enables:
> - At end user level: The ability to launch multiple applications
> simultaneously and paste and cut data between them making productivity
> jumping far ahead.
> - At IT staff level the ability to specialize computers in server or client
> (workstation) role, to simplify user care and deployment of new applications
> lowering TCO.
> - The use of more abstracted programming paradigm, COM/Corba, simple Object
> languages with garbage collectors like Java, lowering the cost of
> developpement, script languages with dynamic and/or weak typing that are
> awful to a computer scientist but understandable by a mere human being.
>
> As users and managers waited for communicating processes and/or computers,
> complex CPU where produced.
> These CPU where able to enable processes to communicate in a (relatively)
> secure manner.
> Pentium IV is an incredible giant when you compare it to a PDP11.
> It's not fair to compare Minix CPU model with a PentiumIV.
> Minix is more oriented toward appliances (only one application running
> without needing care or administration) and education.
>
> A good description of this all is there:
> http://www.prenhall.com/divisions/es...e/right_3.html
>
> One final thing, I am not sure that the OS design culminates with Posix
> compliant with internal Coba and (X-)Windows of the infernal duo
> Windows/Linux.
> In fact I find Linux boring in it's cloning obsession (after Unix, now its
> more and more MS Windows-ish).
> It remains to see if it have any interest to work at improving OS design
> with today's Googlarization of IT.
>
> One good thing that Minix can bring is putting very different research ideas
> of this century, like Multimedia Roma OS, on a larger audience.
> Other research ideas would be Semantic Web integration at the OS level.
> In the past interesting OSes have also been killed by Unix, like Pick OS,
> where there was no file system but a huge database. Unfortunately you had to
> learn programming and Database to use it. But if you combine a modern
> requesting UI with that idea it's quite funny.
> Other ideas would be to make tiny OS inside bigger OS to tackle with
> unsecure tasks like browsing the Web.
> (please don't mention Plan9 or grid computing :-)
>
> Jean-Pierre
>
>
> "Bernhard Kast" a écrit dans le message de
> news:43922fce$0$708$79720d31@newsreader.inode.at.. .
>
>>Hi!
>>
>>I am not quite sure, why the servers and the user
>>applications run in the same privilege level of
>>the cpu.
>>Taking a look at the Intel Architecture Manuals,
>>I would say it is cheaper (no privilege check,
>>no stack switch) for user level processes to
>>interact with the servers and/or it is just
>>not necessary to have them run in different
>>levels.
>>Or is it for compability reasons? (I don't think
>>so.)
>>
>>ftp://download.intel.com/design/Pent...s/25366517.pdf
>>page 160-162
>>from here:
>>http://www.intel.com/design/pentium4.../index_new.htm
>>
>>thx in advance
>>Bernhard
>
>
>

In article <4392c88d$0$699$79720d31@newsreader.inode.at>,
Bernhard Kast wrote:
>protect.h
>#define INTR_PRIVILEGE 0 /* kernel and interrupt handlers */
>#define TASK_PRIVILEGE 1 /* kernel tasks */
>#define USER_PRIVILEGE 3 /* servers and user processes */
>
>to be more exactly, why the servers are not running in
>Privilege level 2 (ring 2 for the cpu)?
>(I understand, why the server is not running
>in privilege level 0 and 1.)

Because, servers don't need any additional services from the CPU. Whether a
process is a server or not is kept in the (kernel's) process table. The CPU
doesn't have to be aware of the difference.


--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency