.

But Linux is HORRIBLY inefficient compared to operating systems  
written for the native platform. A typical operation, such as a  
fprintf() will run though hundreds or thousands of instructions, while  
under say, z/VM, it will run though 10's. Or less.

Note that these OS's are pretty much all written in hand crafted  
assembler, which is in large part why they work so efficiently. And  
mainframes do I/O really well. They ain't called "Data Centers In A  
Box" for no reason.

By the way, Linux is darn near ubiquitous on mainframes these days. :)


On Mar 3, 2009, at 7:15 PM, Peter M. Eggers wrote:

> On Wed, Nov 19, 2008 at 12:09 PM, Paul Raulerson <[log in to unmask] 
> >wrote:
>
> <snip>
>
>> The one big problem with Linux is that once you get way down under  
>> the
>> covers, it just isn't very efficient.
>> MPE, VM, ZOS, etc. all blow away Linux in terms of efficiency and  
>> the way
>> they use the hardware,
>> and yet the hardware is so darn fast, you don't really notice how
>> inefficient Linux really is.
>
>
> If you really "get way down under the covers", you would know that  
> Linux can
> be made very efficient on any work load you can think of!  This can  
> be real
> time control system, a network router, a desktop, any size server,  
> or a
> super computer.  There are multiple processes and I/O schedulers  
> that are
> included in the "official" kernel and others from non-official  
> sources.  The
> kernel, and the rest of the operating system can be compiled down to  
> the
> last bit, using only the drivers that you need and using only the  
> operating
> system and application features that you want (see Gentoo Linux).

Peter - you will find my name in some of the Unix kernel code for BSD.  
I know how efficient Unix and Linux can be.
Very efficient indeed.

But, you may not know how efficient mainframes are. They are very much  
like HP3K's - only much more so.

Typically, a small mainframe, one priced in the same range as a  
largish HP3K, can easily support 10K users or more.
A Z10 BC machine running z/VM can run 10's or even 100's of copies of  
Linux, all simultaneously

>
> To state "MPE, VM, ZOS, etc. all blow away Linux in terms of  
> efficiency and
> the way they use the hardware" is not only unsubstantiated by any  
> credible
> tests that I am aware of, but also shows a lack of low level operating
> system knowledge.

Oh, I wouldn't say that. I would say rather that it shows intimated  
knowledge of the platforms.
I make no claims at all to expertise on HP3K's. But I do have a rather  
broad bit of experience on
IBM Mainframes, Unisys (Sperry) 2200's, a bit on Burroughs, Suns, AS/ 
400's, PDP-11's, a raft of embedded systems using
Motorola and PowerPC, RS6000s, and a few other systems, including the  
Aegis kernel. And what I would class as
exposure to a whole bunch of other systems.

I'm not bragging, just pointing out that I am not a mainframe bigot.  
But facts is facts.


>  MPE, VM, and z/OS are written for a single hardware
> architecture families by their manufacturers.  VM isn't even an  
> operating
> system, rather a hypervisor to run other operating systems, CP/CMS in
> particular.

What a load of marleky! z/Vm (to give it's proper and current name) is  
indeed a full operating system. CMS is nothing more than a shell, of  
which there are plenty others. Yes, it provides a hypervisor to run  
guests - or logins. Those logins can certainly be other operating  
systems - including z/VM itself.  However, z/VM was used as an  
interactive timesharing platform since the 1960s.
For all the normal tasks, including word procesing, e-mail,  
spreadsheets, printing, etc. PROFS was a very standard way to do it.


> Both MPE and z/OS do not have GUIs and have very limited driver
> support.  When you strip away all of the GUIs and myriad device  
> drivers
> unneeded for any sized server from Linux,  and then compile  
> optimizing for a
> particular CPU, you have a very lean-and-mean operating system.
>

No - what you really have is psuedo PDP-11 Macro assembler that is  
converted to the native assembly language for the target platform,  
with a whale of a lot of overhead.

First, Unix was written to be rather portable. Linux far more so.  
Efficiently is almost always sacrificed to portability in Linux.
What makes Linux appear efficient is that it is running on really fast  
hardware - link Intel - and the hardware itself is being drive very  
inefficiently. What is the average utilization of the processor on  
even a heavily used Linux system? (Hint, it is why VMWARE is making  
inroads in the data centers.)

Second, when you do strip it down to the bare bones, it isn't very  
useful. Great for running a phone perhaps, but not for handing massive  
data center loads. (And indeed, it turns out Linux does drive phone  
switches very nicely, but then, so did Unix. ESS systems you know... )


> Bottom line is that Linux is as efficient as you (KNOW HOW TO) make  
> it.
> Your statements sound like they came from a Microsoft shill claiming  
> that
> the sky will fall, if you use Linux.
>

Oh phooey- your statements sound to me like you are drinking Eric's  
KoolAid.

Let me put it another way, I love the OS on 3Ks - it looks a LOT like  
Burroughs MCP, which I very much admire.
I think when we get a decent emulator out here, or have the capability  
to port MPE/ix to a current platform,  that it has a real place in the  
current OS pantheon, and will be very popular indeed. (Well, with a  
little marketing that is...)

I run Linux on my mainframe, and do some absolutely knock-you-socks- 
off amazing things with it.
But efficient is a relative term, and relatively speaking, Linux is  
anything but efficient. Indeed, I spend hours each month teaching it  
how to use the machine a bit more efficiently.


> Not that I am complaining mind you, Linux is amazing. But how fast the
>> hardware is is knock-your-socks-off
>> amazing. :)
>
>
> Linux does not need fast hardware to run and run well.  Most home  
> wireless
> routers and modems (DSL and cable) run Linux on very anemic  
> hardware.  Yet,
> Linux is the choice to run the very fastest supercomputer in the  
> world,
> Roadrunner (http://www.top500.org/system/9707), an IBM machine, yet  
> IBM uses
> Linux over their own operating systems (granted, IBM operating  
> systems are
> written for and optimized for mainframe architecture, not  
> supercomputer
> architecture).  IBM mainframes also run a considerable amount of  
> Linux (
> http://www-03.ibm.com/systems/z/os/linux/ and http://tinyurl.com/b2kpeq) 
> .
>

Supercomputing is *not* a mainframe thing; high volume transactional  
processing *is*. Big databases *are*.
Really intensive I/O, *is*.

> If Linux doesn't run efficiently on any architecture, you can blame  
> the
> person installing it, not the Linux kernel, nor operating system built
> around it.
>

Actually, you can blame the Linux kernel. Just as a *simple* example,  
try having the kernel
automatically limit CPU to a runaway process ---  without a kernel  
panic I mean.
Ain't there. Not even in SuSE 11.


> I don't know why I bother anymore.
>

I'm not sure why either. You jumped all over me like white on rice.  
Who has been using you for a punching bag lately?
You do have some points.

Spirited Discussion is fun. The way you jumped me ain't.

Peace -

> Peter
>
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