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:

quoted

From: David Hildenbrand
Sent: November 14, 2018 at 9:16:58 PM GMT

quoted

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