Re: [Xen-devel] [BUG] Xen-ballooned memory never returned to domain after partial-free

[Nicholas Tsirakis <niko.tsirakis@xxxxxxxxx>]

>> Do you happen to know the answer to my second question? It's not as 
>> important,
>> but it does confuse me as I wouldn't expect the total memory to be
>> balloon-able at
>> all with the hotplugging configs disabled.

> Ballooning != hotplugging memory
>
> With memory hotplug you can add (or - in theory - remove) memory to the
> kernel it didn't know about before.
>
> With ballooning you just give some memory back to the hypervisor, but
> kernel still has some knowledge about it (e.g. keeps struct page for
> each ballooned memory page).

Got it, thanks for that clarification and for all your help!

--Niko

On Thu, Dec 12, 2019 at 9:21 AM Jürgen Groß <jgross@xxxxxxxx> wrote:
>
> On 12.12.19 15:10, Nicholas Tsirakis wrote:
> >> And I think this is the problem. We want here:
> >>
> >>      balloon_stats.target_pages = balloon_stats.current_pages +
> >>                                   balloon_stats.target_unpopulated;
> >
> > Ahh I knew I was missing something. Tested the patch, works great! 
> > "Reported by"
> > is fine with me.
>
> Thanks.
>
> >
> > Do you happen to know the answer to my second question? It's not as 
> > important,
> > but it does confuse me as I wouldn't expect the total memory to be
> > balloon-able at
> > all with the hotplugging configs disabled.
>
> Ballooning != hotplugging memory
>
> With memory hotplug you can add (or - in theory - remove) memory to the
> kernel it didn't know about before.
>
> With ballooning you just give some memory back to the hypervisor, but
> kernel still has some knowledge about it (e.g. keeps struct page for
> each ballooned memory page).
>
> HTH, Juergen

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