linux-kernel - Re: [PATCH v2 kernel 0/7] Extend virtio-balloon for fast (de)inflating & fast live migration

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Date:	Tue, 26 Jul 2016 21:55:13 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Liang Li <liang.z.li@...el.com>
Cc:	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
	qemu-devel@...gnu.org, virtio-dev@...ts.oasis-open.org,
	dgilbert@...hat.com, quintela@...hat.com, linux-mm@...ck.org
Subject: Re: [PATCH v2 kernel 0/7] Extend virtio-balloon for fast
 (de)inflating & fast live migration

On Wed, Jun 29, 2016 at 06:32:13PM +0800, Liang Li wrote:
> This patch set contains two parts of changes to the virtio-balloon. 
> 
> One is the change for speeding up the inflating & deflating process,
> the main idea of this optimization is to use bitmap to send the page
> information to host instead of the PFNs, to reduce the overhead of
> virtio data transmission, address translation and madvise(). This can
> help to improve the performance by about 85%.
> 
> Another change is for speeding up live migration. By skipping process
> guest's free pages in the first round of data copy, to reduce needless
> data processing, this can help to save quite a lot of CPU cycles and
> network bandwidth. We put guest's free page information in bitmap and
> send it to host with the virt queue of virtio-balloon. For an idle 8GB
> guest, this can help to shorten the total live migration time from 2Sec
> to about 500ms in the 10Gbps network environment.  

So I'm fine with this patchset, but I noticed it was not
yet reviewed by MM people. And that is not surprising since
you did not copy memory management mailing list on it.

I added linux-mm@...ck.org Cc on this mail but this might not be enough.

Please repost (e.g. [PATCH v2 repost]) copying the relevant mailing list
so we can get some reviews.


> 
> Changes from v1 to v2:
>     * Abandon the patch for dropping page cache.
>     * Put some structures to uapi head file.
>     * Use a new way to determine the page bitmap size.
>     * Use a unified way to send the free page information with the bitmap 
>     * Address the issues referred in MST's comments
> 
> Liang Li (7):
>   virtio-balloon: rework deflate to add page to a list
>   virtio-balloon: define new feature bit and page bitmap head
>   mm: add a function to get the max pfn
>   virtio-balloon: speed up inflate/deflate process
>   virtio-balloon: define feature bit and head for misc virt queue
>   mm: add the related functions to get free page info
>   virtio-balloon: tell host vm's free page info
> 
>  drivers/virtio/virtio_balloon.c     | 306 +++++++++++++++++++++++++++++++-----
>  include/uapi/linux/virtio_balloon.h |  41 +++++
>  mm/page_alloc.c                     |  52 ++++++
>  3 files changed, 359 insertions(+), 40 deletions(-)
> 
> -- 
> 1.8.3.1