From: Michal Hocko <mhocko@kernel.org>
To: Wei Wang <wei.w.wang@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.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, virtio-dev@lists.oasis-open.org,
yang.zhang.wz@gmail.com, quan.xu@aliyun.com
Subject: Re: [PATCH v12 6/8] mm: support reporting free page blocks
Date: Tue, 25 Jul 2017 13:25:13 +0200 [thread overview]
Message-ID: <20170725112513.GD26723@dhcp22.suse.cz> (raw)
In-Reply-To: <59771010.6080108@intel.com>
On Tue 25-07-17 17:32:00, Wei Wang wrote:
> On 07/24/2017 05:00 PM, Michal Hocko wrote:
> >On Wed 19-07-17 20:01:18, Wei Wang wrote:
> >>On 07/19/2017 04:13 PM, Michal Hocko wrote:
> >[...
> >>>All you should need is the check for the page reference count, no? I
> >>>assume you do some sort of pfn walk and so you should be able to get an
> >>>access to the struct page.
> >>Not necessarily - the guest struct page is not seen by the hypervisor. The
> >>hypervisor only gets those guest pfns which are hinted as unused. From the
> >>hypervisor (host) point of view, a guest physical address corresponds to a
> >>virtual address of a host process. So, once the hypervisor knows a guest
> >>physical page is unsued, it knows that the corresponding virtual memory of
> >>the process doesn't need to be transferred in the 1st round.
> >I am sorry, but I do not understand. Why cannot _guest_ simply check the
> >struct page ref count and send them to the hypervisor?
>
> Were you suggesting the following?
> 1) get a free page block from the page list using the API;
No. Use a pfn walk, check the reference count and skip those pages which
have 0 ref count. I suspected that you need to do some sort of the pfn
walk anyway because you somehow have to evaluate a memory to migrate,
right?
> 2) if page->ref_count == 0, send it to the hypervisor
yes
> Btw, ref_count may also change at any time.
>
> >Is there any
> >documentation which describes the workflow or code which would use your
> >new API?
> >
>
> It's used in the balloon driver (patch 8). We don't have any docs yet, but
> I think the high level workflow is the two steps above.
I will have a look.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-07-25 11:25 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-12 12:40 [PATCH v12 0/8] Virtio-balloon Enhancement Wei Wang
2017-07-12 12:40 ` [PATCH v12 1/8] virtio-balloon: deflate via a page list Wei Wang
2017-07-12 12:40 ` [PATCH v12 2/8] virtio-balloon: coding format cleanup Wei Wang
2017-07-12 12:40 ` [PATCH v12 3/8] Introduce xbitmap Wei Wang
2017-07-12 12:40 ` [PATCH v12 4/8] xbitmap: add xb_find_next_bit() and xb_zero() Wei Wang
2017-07-12 12:40 ` [PATCH v12 5/8] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-07-12 13:06 ` Michael S. Tsirkin
2017-07-12 13:29 ` Wei Wang
2017-07-12 13:56 ` Michael S. Tsirkin
2017-07-13 7:42 ` Wei Wang
2017-07-13 20:19 ` Michael S. Tsirkin
2017-07-14 7:12 ` Wei Wang
2017-07-23 1:45 ` Michael S. Tsirkin
2017-07-26 3:48 ` Wei Wang
2017-07-26 17:02 ` Michael S. Tsirkin
2017-07-27 2:50 ` Wei Wang
2017-07-28 23:08 ` Michael S. Tsirkin
2017-07-29 12:47 ` Wei Wang
2017-07-30 4:22 ` Michael S. Tsirkin
2017-07-30 5:59 ` Wang, Wei W
2017-07-30 16:18 ` Michael S. Tsirkin
2017-07-30 16:20 ` Michael S. Tsirkin
2017-07-31 12:36 ` Wei Wang
2017-07-13 0:44 ` Michael S. Tsirkin
2017-07-13 1:16 ` kbuild test robot
2017-07-13 4:21 ` kbuild test robot
2017-07-28 8:25 ` Wei Wang
2017-07-28 23:01 ` Michael S. Tsirkin
2017-07-12 12:40 ` [PATCH v12 6/8] mm: support reporting free page blocks Wei Wang
2017-07-13 0:33 ` Michael S. Tsirkin
2017-07-13 8:25 ` Wei Wang
2017-07-14 12:30 ` Michal Hocko
2017-07-14 12:54 ` Michal Hocko
2017-07-14 15:46 ` Michael S. Tsirkin
2017-07-14 19:17 ` Michael S. Tsirkin
2017-07-17 15:24 ` Michal Hocko
2017-07-18 2:12 ` Wei Wang
2017-07-19 8:13 ` Michal Hocko
2017-07-19 12:01 ` Wei Wang
2017-07-24 9:00 ` Michal Hocko
2017-07-25 9:32 ` Wei Wang
2017-07-25 11:25 ` Michal Hocko [this message]
2017-07-25 11:56 ` Wei Wang
2017-07-25 12:41 ` Michal Hocko
2017-07-25 14:47 ` Wang, Wei W
2017-07-25 14:53 ` Michal Hocko
2017-07-26 2:22 ` Wei Wang
2017-07-26 10:24 ` Michal Hocko
2017-07-26 11:44 ` Wei Wang
2017-07-26 11:55 ` Michal Hocko
2017-07-26 12:47 ` Wang, Wei W
2017-07-12 12:40 ` [PATCH v12 7/8] mm: export symbol of next_zone and first_online_pgdat Wei Wang
2017-07-13 0:16 ` Michael S. Tsirkin
2017-07-13 8:41 ` [virtio-dev] " Wei Wang
2017-07-14 12:31 ` Michal Hocko
2017-07-12 12:40 ` [PATCH v12 8/8] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ Wei Wang
2017-07-13 0:22 ` Michael S. Tsirkin
2017-07-13 8:46 ` Wei Wang
2017-07-13 17:59 ` Michael S. Tsirkin
2017-07-13 0:14 ` [PATCH v12 0/8] Virtio-balloon Enhancement Michael S. Tsirkin
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