On 7/26/2023 7:54 PM, Sean Christopherson wrote:

On Wed, Jul 26, 2023, Nikunj A. Dadhania wrote:

quoted

On 7/24/2023 10:30 PM, Sean Christopherson wrote:

quoted

quoted

quoted

  /proc/<qemu pid>/smaps
  7f528be00000-7f5c8be00000 rw-p 00000000 00:01 26629                      /memfd:memory-backend-memfd-shared (deleted)
  7f5c90200000-7f5c90220000 rw-s 00000000 00:01 44033                      /memfd:rom-backend-memfd-shared (deleted)
  7f5c90400000-7f5c90420000 rw-s 00000000 00:01 44032                      /memfd:rom-backend-memfd-shared (deleted)
  7f5c90800000-7f5c90b7c000 rw-s 00000000 00:01 1025                       /memfd:rom-backend-memfd-shared (deleted)

This is all expected, and IMO correct.  There are no userspace mappings, and so
not accounting anything is working as intended.

Doesn't sound that correct, if 10 SNP guests are running each using 10GB, how
would we know who is using 100GB of memory?

It's correct with respect to what the interfaces show, which is how much memory
is *mapped* into userspace.

As I said (or at least tried to say) in my first reply, I am not against exposing
memory usage to userspace via stats, only that it's not obvious to me that the
existing VMA-based stats are the most appropriate way to surface this information.

Right, then should we think in the line of creating a VM IOCTL for querying current memory
usage for guest-memfd ?

We could use memcg for statistics, but then memory cgroup can be disabled and so memcg 
isn't really a dependable option.

Do you have some ideas on how to expose the memory usage to the user space other than
VMA-based stats ?

Regards,
Nikunj