Re: The performance and behaviour of the anti-fragmentation related patches

Paul Mackerras
2007-03-06T04:16:33Z

Linus Torvalds writes:

> The point being that in the guests, hotunplug is almost useless (for
> bigger ranges), and we're much better off just telling the virtualization
> hosts on a per-page level whether we care about a page or not, than to
> worry about fragmentation.

We don't have that luxury on IBM System p machines, where the
hypervisor manages memory in much larger units than a page. Typically
the size of memory block that the hypervisor uses to manage memory is
16MB or more -- which makes sense from the point of view that if the
hypervisor had to manage individual pages, it would end up adding a
lot more overhead than it does.

Paul.