Re: [PATCH v1 2/2] Drivers: virtio: balloon: Report inflated memory

[Alexander Atanasov]

On 15.08.22 19:05, Nadav Amit wrote:
> On Aug 15, 2022, at 5:52 AM, Alexander Atanasov <alexander.atanasov@xxxxxxxxxxxxx> wrote:
>
> > If it is going to be a place for generic logic may be it should be
> > renamed to balloon_common.[ch] ?
> >
> > > as possible. I made the effort to reuse this infrastructure (which is now
> > > used by both VMware and virtio), and would prefer to share as much code as
> > > possible.
> > >
> > > For instance, I would appreciate if the update upon inflate would go into
> > > balloon_page_list_enqueue() and balloon_page_enqueue(). VMware's 2MB pages
> > > logic is not shared, so it would require a change that is specific for
> > > VMware code.
> >
> > I looked at the code and i do not see how i can reuse it since
> > BALLOON_COMPACTION can be disabled and as you say even for VMWare it
> > would require updates on other places. Looks like if i do so i would
> > have to handle update from each driver for both cases. I think it is
> > better to clearly mark the spots when drivers do their internal
> > recalculations and report to the core. I see only VMWare is using
> > balloon_page_list_enqueue , virtio balloon is using only migration and
> > i don't see how to hook it there - i haven't checked the rest of the
> > balloons but i guess it would be similiar . I agree it is a good to have
> > a common place for such logic but it might be better of for a separate
> > work in the future.
>
> Fine. I would live with whatever you do and if needed change it later.


- balloon_page_list_enqueue and balloon_page_enqueue are called under locks.
- they work page by page
- different page sizes different hypervisors
- pages to bytes conversion again different page sizes

I will put the new code in balloon_common but i can not reuse what you 
propose for the reasons above.

--
Regards,
Alexander Atanasov