[Info-vax] Kernel Transplantation (was: Re: New CEO of VMS Software)

[Lawrence D'Oliveiro]

On Sat, 6 Jan 2024 13:36:59 -0500, Stephen Hoffman wrote:

> On 2024-01-06 02:48:42 +0000, Lawrence D'Oliveiro said:
> 
>> That can be blamed on the limitations of Mach. People still seem to
>> think microkernels are somehow a good idea, but they really don’t help
>> much, do they?
> 
> With current hardware including cores and performance and with newer
> message-passing designs such as OKL4 and ilk, some things are looking
> rather better.

Hope springs eternal in the microkernel aficionado’s breast. ;)

>>> As another example, it was not possible to emulate VMS’ strong
>>> isolation of kernel resource usage by different users.
>> 
>> Would the Linux cgroups functionality (as commonly used in the various
>> container schemes) help with this?
> 
> No.
> 
> Designers of VAX/VMS chose a memory management model closer to that of
> Multics, where much of the rest of hardware and software in the industry
> diverged from that lotsa-rings memory management design.

Seems you are confusing two different things here. I am aware of the user/
supervisor/exec/kernel privilege-level business, but you did say “resource 
usage by different *users*”. cgroups are indeed designed to manage that.

Remember that my proposal for adopting the Linux kernel would get rid of 
every part of VMS that currently runs at higher than user mode. It’s only 
their own user-mode code that customers would care about.

> Containers are arguably fundamentally about product-licensing arbitrage,
> too.

I don’t use them that way. I use them as a cheap way to run up multiple 
test installations of things I am working on, instead of resorting to full 
VMs. Typically it only takes a few gigabytes to create a new userland for 
a container. E.g. on this machine I am using now:

    root at theon:~ # du -ks /var/lib/lxc/*/rootfs/
    1700060 /var/lib/lxc/debian10/rootfs/
    7654028 /var/lib/lxc/debian11/rootfs/
    876568  /var/lib/lxc/debian12/rootfs/

> Microkernels are in use all over the place nowadays, seL4-, L4-, and
> OKL4-derived.

Really?? Can you name some deployments? How would performance compare with 
Linux? Because, let’s face it, Linux is the standard for high-performance 
computing.

> For a small development team—and VSI is tiny—kernel transplantation
> doesn't gain much from a technical basis, once the platform port is
> completed. It might help with future ports, sure.

Which was my point all along: if they’d done this for the AMD64 port from 
the beginning, they would have shaved *years* off the development time.
And likely ended up with a somewhat larger (remaining) customer base than 
they have now.