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

[Gavin Shan <gshan@redhat.com>]

Hi Pasha,

On 2/21/23 3:31 AM, Pasha Tatashin wrote:
> 
> As a part of an ongoing work of replacing some containerized work load
> with virtual machines within Google, I have worked on making the
> memory translations faster.
> 
> I would like to propose the following topic for this year's LSF/MM/BPF:
> 
> Discuss  a set of techniques that can improve the guest performance,
> memory footprint overhead, observability, and manageability of virtual
> machines by hypervirtualizing the guest memory to the extreme. The end
> goal is to allow very lightweight virtual machines to be closer in
> performance to the containers.
> 
> The following items are going to be discussed in this topic:
> - Reducing the cost of SLAT page table translations.
> - Reducing the memory footprint overhead.
> - Reducing the memory management overhead.
> - Increasing the observability of guest memory.
> 

It's all about to understand the problem and possible solution or directions.

I googled for 'SLAT' and direct me to x86's EPT. ARM64 has similar thing called
stage-2 page table. The usual way to reduce page table translation cost is to map
the contiguous memory through PUD/PMD. I'm not sure if there are other solutions
we're heading for?

Guest's memory is usually backed up by virtual memory area (VMA), which is either
a anonymous or hugetlb region. As I understand, the page fault handling is excessive
to populate the requested memory. I'm not sure if reducing the memory management
overhead is to get it faster, or something else? :)

Thanks,
Gavin