Re: [Ksummit-discuss] ZONE_DEVICE and Persistent Memory (was: Re: Draft agenda for the kernel summit)

[Theodore Ts'o <tytso@mit.edu>]

On Fri, Oct 16, 2015 at 05:08:21PM -0400, Jerome Glisse wrote:
> On Thu, Oct 15, 2015 at 09:49:49AM -0700, Dave Hansen wrote:
> > On 10/14/2015 05:17 PM, Dan Williams wrote:
> > > I am wondering if it would be productive / good use of time to do a
> > > direction check on the mm changes being done in support of large
> > > persistent memory devices.
> > 
> > I think there's probably an even wider discussion that we should have here.
> > 
> > Beyond just ZONE_DEVICE, the sheer number of memory types is increasing
> > fast, and our current solutions are, at best, inconsistent. We currently
> > handle memory types as new zones, repurposed zones, pageblocks inside
> > zones, or faux NUMA nodes.
> > 
> > Are our current solutions too erratic?
> > Do we need to solve these problems generally, or are we going to kill
> > ourselves trying to make everyone happy?
> > What types do we ignore today, but shouldn't?
> > What types are coming down the pike?
> 
> I think what i am working on (HMM and how to leverage GPU memory that is
> not accessible by the CPU) apply here too. All features i am working on
> imply that i have to dig through layers of code seeing if i can abuse an
> existing mechanism to achieve something new.
> 
> So i definitly think we should discuss where we are and where we want to
> be.

Dan, would you be willing to kick off the discussion?

							- Ted