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

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Hi Alan --

Sorry, I'm not trying to be cryptic.  I'm having some network
problems and will try to post the Linux patch shortly.

I'm aware of IBM's CMM and I think (hope) tmem achieves similar
goals but is much much simpler and more extensible for other
interesting uses.  After I get the patch posted, let me know
if you agree.

Yes, one of the other uses for tmem is for cluster nodes
co-resident on a physical machine to share a "virtual page
cache".  That's under development... working with the ocfs2
team.

Looking forward to more discussion...

Dan

> > 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.

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