linux-kernel - Re: [PATCH v37 0/3] Virtio-balloon: support free page reporting

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Message-ID: <5BD1988D.7010606@intel.com>
Date:   Thu, 25 Oct 2018 18:18:53 +0800
From:   Wei Wang <wei.w.wang@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     virtio-dev@...ts.oasis-open.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, mhocko@...nel.org, akpm@...ux-foundation.org,
        dgilbert@...hat.com, torvalds@...ux-foundation.org,
        pbonzini@...hat.com, liliang.opensource@...il.com,
        yang.zhang.wz@...il.com, quan.xu0@...il.com, nilal@...hat.com,
        riel@...hat.com, peterx@...hat.com, quintela@...hat.com
Subject: Re: [PATCH v37 0/3] Virtio-balloon: support free page reporting

On 10/25/2018 08:58 AM, Michael S. Tsirkin wrote:
> On Mon, Aug 27, 2018 at 09:32:16AM +0800, Wei Wang wrote:
>> The new feature, VIRTIO_BALLOON_F_FREE_PAGE_HINT, implemented by this
>> series enables the virtio-balloon driver to report hints of guest free
>> pages to host. It can be used to accelerate virtual machine (VM) live
>> migration. Here is an introduction of this usage:
>>
>> Live migration needs to transfer the VM's memory from the source machine
>> to the destination round by round. For the 1st round, all the VM's memory
>> is transferred. From the 2nd round, only the pieces of memory that were
>> written by the guest (after the 1st round) are transferred. One method
>> that is popularly used by the hypervisor to track which part of memory is
>> written is to have the hypervisor write-protect all the guest memory.
>>
>> This feature enables the optimization by skipping the transfer of guest
>> free pages during VM live migration. It is not concerned that the memory
>> pages are used after they are given to the hypervisor as a hint of the
>> free pages, because they will be tracked by the hypervisor and transferred
>> in the subsequent round if they are used and written.
> OK so it will be in linux-next.  Now can I trouble you for a virtio spec
> patch with the description please?

No problem, I'll start to patch the spec. Thanks!

Best,
Wei