The point of virtualization [LWN.net]

The point of virtualization

Posted Oct 12, 2007 23:02 UTC (Fri) by roelofs (subscriber, #2599)
In reply to: The point of virtualization by roelofs
Parent article: Matt Domsch on Linux support at Dell

Those are probably included in my phrasing, "a system built for virtualization." And they're upcoming only for the Intel stuff.

OK, maybe I didn't go back far enough for context. I think I now see what you meant by "a system built for virtualization"--you were implicitly excluding the extra set of memory accesses due to shadow page tables in software-based virtualization. But I misread that since you were replying to the author's comment about existing Dell hardware--which explicitly does not include IBM mainframe technologies. And your original statement was a flat denial of any performance penalty due to virtualization ("The virtualization layer doesn't slow the machine down, anyway."). It was more that part to which I was replying.

Greg

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The point of virtualization

Posted Oct 13, 2007 2:31 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

I agree the answer to the question, "does virtualization slow systems down" is different if one means virtualization per se than if one means virtualization in practice.

In the original comment, I thought I saw questioning of the very concept of virtualization -- i.e. why is everyone rushing toward this thing if it costs so much speed? So in addition to pointing out what I think the benefits are supposed to be, I also opined that it doesn't cost speed. I think the virtualization that people are presenting as the next big thing is virtualization done right, not necessarily what is practical today. E.g. companies are introducing new products specifically to enable virtualization.