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Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration

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On 04/14/2017 09:50 AM, Michael S. Tsirkin wrote:
> On Thu, Apr 13, 2017 at 01:44:11PM -0700, Matthew Wilcox wrote:
>> On Thu, Apr 13, 2017 at 05:35:03PM +0800, Wei Wang wrote:
>>> 2) transfer the guest unused pages to the host so that they
>>> can be skipped to migrate in live migration.
>> I don't understand this second bit.  You leave the pages on the free list,
>> and tell the host they're free.  What's preventing somebody else from
>> allocating them and using them for something?  Is the guest semi-frozen
>> at this point with just enough of it running to ask the balloon driver
>> to do things?
> There's missing documentation here.
>
> The way things actually work is host sends to guest
> a request for unused pages and then write-protects all memory.
>
> So guest isn't frozen but any changes will be detected by host.
>

Probably it's better to say " transfer the info about the guest unused pages
to the host so that the host gets a chance to skip the transfer of the 
unused
pages during live migration".

Best,
Wei

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[PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration Wei Wang <wei.w.wang@intel.com> - 2017-04-13 11:50 +0200
  [PATCH v9 5/5] virtio-balloon: VIRTIO_BALLOON_F_MISC_VQ Wei Wang <wei.w.wang@intel.com> - 2017-04-13 11:50 +0200
    Re: [PATCH v9 5/5] virtio-balloon: VIRTIO_BALLOON_F_MISC_VQ "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-13 19:10 +0200
  [PATCH v9 3/5] mm: function to offer a page block on the free list Wei Wang <wei.w.wang@intel.com> - 2017-04-13 11:50 +0200
    Re: [PATCH v9 3/5] mm: function to offer a page block on the free  list Andrew Morton <akpm@linux-foundation.org> - 2017-04-13 22:10 +0200
      Re: [PATCH v9 3/5] mm: function to offer a page block on the free  list Wei Wang <wei.w.wang@intel.com> - 2017-04-14 04:30 +0200
        Re: [PATCH v9 3/5] mm: function to offer a page block on the free  list Matthew Wilcox <willy@infradead.org> - 2017-04-14 05:00 +0200
          Re: [PATCH v9 3/5] mm: function to offer a page block on the free  list Wei Wang <wei.w.wang@intel.com> - 2017-04-14 11:00 +0200
  [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS Wei Wang <wei.w.wang@intel.com> - 2017-04-13 11:50 +0200
    Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-13 18:40 +0200
      Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS Matthew Wilcox <willy@infradead.org> - 2017-04-13 19:10 +0200
      Re: [virtio-dev] Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS Wei Wang <wei.w.wang@intel.com> - 2017-04-14 10:40 +0200
        Re: [virtio-dev] Re: [PATCH v9 2/5] virtio-balloon:  VIRTIO_BALLOON_F_BALLOON_CHUNKS "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-14 23:40 +0200
          Re: [virtio-dev] Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS Wei Wang <wei.w.wang@intel.com> - 2017-04-17 05:40 +0200
  Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration Matthew Wilcox <willy@infradead.org> - 2017-04-13 22:50 +0200
    Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-14 04:00 +0200
      Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration Wei Wang <wei.w.wang@intel.com> - 2017-04-14 04:30 +0200
        Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-14 05:00 +0200
      Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration Matthew Wilcox <willy@infradead.org> - 2017-04-14 11:50 +0200
        Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating &  fast live migration "Michael S. Tsirkin" <mst@redhat.com> - 2017-04-14 16:30 +0200

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