Re: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically offline

Nadav Amit
2018-11-14T23:41:16Z

From: David Hildenbrand
Sent: November 14, 2018 at 11:05:38 PM GMT
> Subject: Re: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically offline
>
>
> On 14.11.18 23:57, Nadav Amit wrote:
>> From: David Hildenbrand
>> Sent: November 14, 2018 at 9:16:58 PM GMT
>>> Subject: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically offline
>>>
>>>
>>> Right now, pages inflated as part of a balloon driver will be dumped
>>> by dump tools like makedumpfile. While XEN is able to check in the
>>> crash kernel whether a certain pfn is actuall backed by memory in the
>>> hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of
>>> virtio-balloon and hv-balloon inflated memory will essentially result in
>>> zero pages getting allocated by the hypervisor and the dump getting
>>> filled with this data.
>>
>> Is there any reason that VMware balloon driver is not mentioned?
>
> Definitely ...
>
> ... not ;) . I haven't looked at vmware's balloon driver yet (I only saw
> that there was quite some activity recently). I guess it should have
> similar problems. (I mean reading and dumping data nobody cares about is
> certainly not desired)
>
> Can you share if something like this is also desired for vmware's
> implementation? (I tagged this as RFC to get some more feedback)
>
> It should in theory be as simple as adding a handful of
> _SetPageOffline()/_ClearPageOffline() at the right spots.

Thanks, I was just suspecting it is personal ;-)

Actually, some patches that I sent for 4.20 to use the balloon-compaction
infrastructure by the VMware balloon fell between the cracks, and I need
to resend them.

I would obviously prefer that your changes would be done on top of those
that were skipped. This patch-set sounds very reasonable to me, but I prefer
that Julien (cc’d) would also give his opinion.

Regards,
Nadav