Re: [LSF/MM/BPF TOPIC] Virtual Machine Memory Passthrough

[Pasha Tatashin <pasha.tatashin@soleen.com>]

> Coming from the virtio-pmem and some free page hinting background, I am
> interested in this discussion. I saw your proposal about single owner
> memory driver in other thread and could not entirely link the dots about
> applicability of the idea with "reducing the memory footprint overhead
> for virtual machines". Do we plan to co-ordinate guest memory state with
> corresponding host state for efficient memory reclaim decisions?
> Or something entirely different we are targeting here?

Hi Pankaj,

The plan is to have a driver /dev/memctl and corresponding VMM agent
that synchronously passes information about how guest would like its
memory to be backed on the host.

For example the following information can come from guest for a range
of physical addresses:
MADV_NOHUGEPAGE
MADV_HUGEPAGE
MADV_DONTNEED
PR_SET_VMA_ANON_NAME
etc.

All together this should help by doing memory management operations
only on the host side, and reduce the number of operations that are
performed on the guest.

The /dev/som can help with allowing support for anonymous memory in
the guest with 1G pages that are only partially backed on the host
side, thus yielding to faster guestVA hostPA translations.

Pasha