Re: [PATCH v21 1/4] mm: add VM_DROPPABLE for designating always lazily freeable mappings

[David Hildenbrand <david@redhat.com>]

> As a side note, I'll raise that I am not a particular fan of the
> "droppable" terminology, at least with the "read 0s" approach.
> 
>   From a user perspective, the memory might suddenly lose its state and
> read as 0s just like volatile memory when it loses power. "dropping
> pages" sounds more like an implementation detail.

Just to raise why I consider "dropping" an implementation detail: in 
combination with a previous idea I had of exposing "nonvolatile" memory 
to VMs, the following might be interesting:

A hypervisor could expose special "nonvolatile memory" as separate guest 
physical memory region to a VM.

We could use that special memory to back these MAP_XXX regions in our 
guest, in addition to trying to make use of them in the guest kernel, 
for example for something similar to cleancache.

Long story short: it's the hypervisor that could be effectively 
dropping/zeroing out that memory, not the guest VM. "NONVOLATILE" might 
be clearer than "DROPPABLE".

But again, naming is hard ... :)

-- 
Cheers,

David / dhildenb