Re: [RFC] Virtualizing tagged disaggregated memory capacity (app specific, multi host shared)

Jonathan Cameron
2024-08-16T09:41:14Z

On Fri, 16 Aug 2024 09:05:46 +0200
Hannes Reinecke <hare@suse.de> wrote:

> On 8/15/24 18:22, Jonathan Cameron wrote:
> > Introduction
> > ============
> >
> > If we think application specific memory (including inter-host shared memory) is
> > a thing, it will also be a thing people want to use with virtual machines,
> > potentially nested. So how do we present it at the Host to VM boundary?
> >
> > This RFC is perhaps premature given we haven't yet merged upstream support for
> > the bare metal case. However I'd like to get the discussion going given we've
> > touched briefly on this in a number of CXL sync calls and it is clear no one is
> > entirely sure what direction make sense. We may briefly touch on this in the
> > LPC CXL uconf, but time will be very limited.
> >
> Thanks for the detailed write-up.
>
> Can't we have an ad-hoc meeting at OSS/LPC to gather interested/relevant
> people to explore ideas around this?

Absolutely. If people want to email me directly (or mention in the thread)
I'll gather up a list of people to try and find a suitable time / place
(and then post that here).

>
> In particular I'd be interested on how to _get_ the application specific
> memory to the application in question. It's easy if you have your own
> application and design it to work on DAX devices. Obviously this
> approach won't work for unmodified applications; however, they really
> might want to use this, too.

That's a good parallel question (as not virtualization specific).
I'd be tempted to enable this path first for aware applications, but longer
term the ability to use this via common allocator libraries (LD_PRELOAD etc)
might make sense (or some other path?)

>
> And, of course, the other mentioned problems are worth discussing, and I
> do agree that the uconf will probably not providing sufficient time for
> this.
>
> Cheers,
>
> Hannes