Linked by SReilly on Thu 18th Feb 2010 22:37 UTC
Hardware, Embedded Systems OSNews recently linked to several articles on the two remaining big iron RISC based platforms still alive and kicking, something of great interest to myself both in a professional capacity and for personal reasons (I wouldn't be an avid OSNews reader and poster if I wasn't into non mainstream architectures).
Permalink for comment 410287
To read all comments associated with this story, please click here.
Paravirtualization
by Mark Williamson on Sun 21st Feb 2010 18:04 UTC
Mark Williamson
Member since:
2005-07-06

I liked the article, thank you. The Big Iron ISAs are cool but it's interesting / amazing to see the other technology that these large systems have had for years that is still trickling down slowly to commodity systems. It's fascinating to learn more about the capabilities of large systems; there's a lot to learn there and the majority of folks using commodity hardware rarely get to hear about it. People perhaps think of a large, lumbering mainframe but don't realise just how advanced some of this stuff still is...

I have one main quibble: Paravirtualization (or sometimes paravirtualisation in the UK) generally refers to modifications that expose virtualisation to the guest. That can involve modifications to the guest's low-level architecture dependent code or to device drivers. If the guest thinks it's talking to a real hardware device then that's still full virtualisation / emulation of that device, regardless of how the VMM is actually providing that device. So providing a host OS file to the guest as a hard drive is still actually full virtualisation unless you've installed virtualisation-aware drivers into the guest.

Currently, PCIe devices already support multiple functions but so far this has been used to support different hardware capabilities.


I believe that this statement is slightly behind the state-of-the-art though I may be confused. The IO Virtualisation specs for PCI do allow a somewhat standardised way to export multiple virtual interfaces from a single PCI device.

A few devices that predate this spec also defined their own ways to export multiple virtual interfaces so that similar functionality has been available for a while now. This gets used to provide safe direct hardware access to virtual machines and to unprivileged applications. It's still not that common, though, whereas I presume Big Iron makes equivalent functionality somewhat ubiquitous!

The scary thing is just how far ahead the likes of IBM have been; x86 systems are still catching up to some features that have been available on IBM's large systems for decades. And that's ignoring the integration advantages of buying hardware, OS and support from one company. Not forgetting the extreme Ninja-ness of the support that the really serious vendors provide. I knew a guy whose university acquired an IBM mainframe in a competition; part of the deal involved a dedicated telephone line between the mainframe and IBM. They reconfigured storage and before they knew it they had a phonecall from IBM saying "Your mainframe says there's a problem". That's service!

Reply Score: 2