Re: [Xen-devel] [RFC] Transcendent Memory ("tmem"): a new approach to physical memory management

[Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>]

> Comments and questions welcome.  I also plan to submit an
> abstract for the upcoming Xen summit and, if accepted, give
> a talk about tmem there.

I assume you've looked at how S/390 handles this problem - the guests can
mark pages as stable or unused and the rest is up to the hypervisor ? No
complex pool interfaces and the resulting interface slots into the Linux
kernel as a pair of 1 liners in existing arch_foo hooks in the mm. The
S/390 keeps the question of shared/private memory objects separate from
the question of whether they are currently used - a point on which I
think their model and interface is probably better.

I would look at the patches but the URL you give contains nothing but an
empty repository. I'd be interested to see how the kernel patches look
and also how you implement migration of some of the users of a shared
pool object - do you implement a full clustered memory manager and what do the
performance figures look like across networks ? How do you find a pool
across the network ?

Its interesting as you can do a lot of other interesting things with this
kind of interface. Larry McVoy's bitcluster SMP proposal was built on a
similar idea using refcounted page loans to drive a multiprocessor NUMA
box as a cluster with page sharing.

Alan

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