Re: [RFC 1/5] meminfo: add a per node counter for balloon drivers

[David Hildenbrand]

On 13.03.25 18:35, Nico Pache wrote:
> On Thu, Mar 13, 2025 at 2:22 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
> > On 13.03.25 00:04, Nico Pache wrote:
> > > On Wed, Mar 12, 2025 at 4:19 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
> > > > On 12.03.25 01:06, Nico Pache wrote:
> > > > > Add NR_BALLOON_PAGES counter to track memory used by balloon drivers and
> > > > > expose it through /proc/meminfo and other memory reporting interfaces.
> > > >
> > > > In balloon_page_enqueue_one(), we perform a
> > > >
> > > > __count_vm_event(BALLOON_INFLATE)
> > > >
> > > > and in balloon_page_list_dequeue
> > > >
> > > > __count_vm_event(BALLOON_DEFLATE);
> > > >
> > > >
> > > > Should we maybe simply do the per-node accounting similarly there?
> > >
> > > I think the issue is that some balloon drivers use the
> > > balloon_compaction interface while others use their own.
> > >
> > > This would require unifying all the drivers under a single api which
> > > may be tricky if they all have different behavior
> >
> > Why would that be required? Simply implement it in the balloon
> > compaction logic, and in addition separately in the ones that don't
> > implement it.
>
> Ah ok that makes sense!
>
> > That's the same as how we handle PageOffline today.
> >
> > In summary, we have
> >
> > virtio-balloon: balloon compaction
> > hv-balloon: no balloon compaction
> > xen-balloon: no balloon compaction
> > vmx-balloon: balloon compaction
> > pseries-cmm: balloon compaction
>
> I'm having a hard time verifying this... it looks like only
> vmx-balloon uses the balloon_compaction balloon_page_list_enqueue
> function that calls balloon_page_enqueue_one.

Also check balloon_page_enqueue, which ends up calling 
balloon_page_enqueue_one.

> > So you'd handle 3 balloon drivers in one go.
> >
> > (this series didn't touch pseries-cmm)
> Ah I didn't realize that was a balloon driver. Ill add that one to the todo.


Well, by implementing it in the compaction code that todo would be done :)

--
Cheers,

David / dhildenb