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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Wei Wang <wei.w.wang@intel.com>,
	linux-kernel@vger.kernel.org, qemu-devel@nongnu.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-mm@kvack.org, david@redhat.com, cornelia.huck@de.ibm.com,
	akpm@linux-foundation.org, mgorman@techsingularity.net,
	aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com,
	liliang.opensource@gmail.com
Subject: Re: [PATCH v11 4/6] mm: function to offer a page block on the free list
Date: Mon, 12 Jun 2017 23:34:06 +0300	[thread overview]
Message-ID: <20170612194438-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <9d0900f3-9df5-ac63-4069-2d796f2a5bc7@intel.com>

On Mon, Jun 12, 2017 at 09:42:36AM -0700, Dave Hansen wrote:
> On 06/12/2017 09:28 AM, Michael S. Tsirkin wrote:
> > 
> >> The hypervisor is going to throw away the contents of these pages,
> >> right?
> > It should be careful and only throw away contents that was there before
> > report_unused_page_block was invoked.  Hypervisor is responsible for not
> > corrupting guest memory.  But that's not something an mm patch should
> > worry about.
> 
> That makes sense.  I'm struggling to imagine how the hypervisor makes
> use of this information, though.  Does it make the pages read-only
> before this, and then it knows if there has not been a write *and* it
> gets notified via this new mechanism that it can throw the page away?

Yes, and specifically, this is how it works for migration.  Normally you
start by migrating all of memory, then send updates incrementally if
pages have been modified.  This mechanism allows skipping some pages in
the 1st stage, if they get changed they will be migrated in the 2nd
stage.

-- 
MST

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  reply	other threads:[~2017-06-12 20:34 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-09 10:41 [PATCH v11 0/6] Virtio-balloon Enhancement Wei Wang
2017-06-09 10:41 ` [PATCH v11 1/6] virtio-balloon: deflate via a page list Wei Wang
2017-06-09 10:41 ` [PATCH v11 2/6] virtio-balloon: coding format cleanup Wei Wang
2017-06-09 10:41 ` [PATCH v11 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE_CHUNKS Wei Wang
2017-06-13 17:56   ` Michael S. Tsirkin
2017-06-13 17:59     ` Dave Hansen
2017-06-13 18:55       ` Michael S. Tsirkin
2017-06-15  8:10     ` [virtio-dev] " Wei Wang
2017-06-16  3:19       ` Michael S. Tsirkin
2017-06-28 15:04       ` Matthew Wilcox
2017-07-12 13:05         ` Wei Wang
2017-06-09 10:41 ` [PATCH v11 4/6] mm: function to offer a page block on the free list Wei Wang
2017-06-12 14:10   ` Dave Hansen
2017-06-12 16:28     ` Michael S. Tsirkin
2017-06-12 16:42       ` Dave Hansen
2017-06-12 20:34         ` Michael S. Tsirkin [this message]
2017-06-12 20:54           ` Dave Hansen
2017-06-13  2:56             ` Wei Wang
2017-06-20 16:44     ` Rik van Riel
2017-06-20 16:49       ` David Hildenbrand
2017-06-20 17:29         ` Rik van Riel
2017-06-20 18:26           ` Michael S. Tsirkin
2017-06-20 19:51             ` Rik van Riel
2017-06-21 12:41               ` Michael S. Tsirkin
2017-06-21  8:38           ` [Qemu-devel] " Wei Wang
2017-06-20 18:17         ` Michael S. Tsirkin
2017-06-20 18:54           ` David Hildenbrand
2017-06-20 18:56             ` Michael S. Tsirkin
2017-06-20 19:01               ` David Hildenbrand
2017-06-21 12:56         ` Christian Borntraeger
2017-06-21 13:47           ` David Hildenbrand
2017-06-09 10:41 ` [PATCH v11 5/6] mm: export symbol of next_zone and first_online_pgdat Wei Wang
2017-06-09 10:41 ` [PATCH v11 6/6] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ Wei Wang
2017-06-12 14:07   ` Dave Hansen
2017-06-13 10:17     ` Wei Wang
2017-06-20 16:18   ` Michael S. Tsirkin
2017-06-21  3:28     ` [virtio-dev] " Wei Wang
2017-06-21 12:28       ` Michael S. Tsirkin
2017-06-22  8:40         ` Wei Wang
2017-06-28 15:01           ` Michael S. Tsirkin
2017-07-12 12:57             ` Wei Wang
2017-06-09 11:18 ` [PATCH v11 0/6] Virtio-balloon Enhancement Wang, Wei W

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