From: "Wang, Wei W" <wei.w.wang@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "virtio-dev@lists.oasis-open.org"
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Subject: RE: [PATCH v10 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE_CHUNKS
Date: Sun, 7 May 2017 04:22:46 +0000 [thread overview]
Message-ID: <286AC319A985734F985F78AFA26841F7391FFBE8@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <20170506012146-mutt-send-email-mst@kernel.org>
On 05/06/2017 06:29 AM, Michael S. Tsirkin wrote:
> On Thu, May 04, 2017 at 04:50:12PM +0800, Wei Wang wrote:
> > Add a new feature, VIRTIO_BALLOON_F_PAGE_CHUNKS, which enables the
> > transfer of the ballooned (i.e. inflated/deflated) pages in chunks to
> > the host.
> >
> > The implementation of the previous virtio-balloon is not very
> > efficient, because the ballooned pages are transferred to the host one
> > by one. Here is the breakdown of the time in percentage spent on each
> > step of the balloon inflating process (inflating 7GB of an 8GB idle
> > guest).
> >
> > 1) allocating pages (6.5%)
> > 2) sending PFNs to host (68.3%)
> > 3) address translation (6.1%)
> > 4) madvise (19%)
> >
> > It takes about 4126ms for the inflating process to complete.
> > The above profiling shows that the bottlenecks are stage 2) and stage
> > 4).
> >
> > This patch optimizes step 2) by transferring pages to the host in
> > chunks. A chunk consists of guest physically continuous pages.
> > When the pages are packed into a chunk, they are converted into
> > balloon page size (4KB) pages. A chunk is offered to the host via a
> > base PFN (i.e. the start PFN of those physically continuous
> > pages) and the size (i.e. the total number of the 4KB balloon size
> > pages). A chunk is formatted as below:
> > --------------------------------------------------------
> > | Base (52 bit) | Rsvd (12 bit) |
> > --------------------------------------------------------
> > --------------------------------------------------------
> > | Size (52 bit) | Rsvd (12 bit) |
> > --------------------------------------------------------
> >
> > By doing so, step 4) can also be optimized by doing address
> > translation and madvise() in chunks rather than page by page.
> >
> > With this new feature, the above ballooning process takes ~590ms
> > resulting in an improvement of ~85%.
> >
> > TODO: optimize stage 1) by allocating/freeing a chunk of pages instead
> > of a single page each time.
> >
> > Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> > Signed-off-by: Liang Li <liang.z.li@intel.com>
> > Suggested-by: Michael S. Tsirkin <mst@redhat.com>
>
>
> This is much cleaner, thanks. It might be even better to have wrappers that put
> array and its size in a struct and manage that struct, but I won't require this for
> submission.
OK, thanks. Would this be your suggestion:
struct virtio_balloon_page_struct {
unsigned int page_bmap_num;
unsigned long *page_bmap[VIRTIO_BALLOON_PAGE_BMAP_MAX_NUM];
}
Best,
Wei
next prev parent reply other threads:[~2017-05-07 21:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-04 8:50 [PATCH v10 0/6] Extend virtio-balloon for fast (de)inflating & fast live migration Wei Wang
2017-05-04 8:50 ` [PATCH v10 1/6] virtio-balloon: deflate via a page list Wei Wang
2017-05-04 8:50 ` [PATCH v10 2/6] virtio-balloon: coding format cleanup Wei Wang
2017-05-04 8:50 ` [PATCH v10 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE_CHUNKS Wei Wang
2017-05-05 22:29 ` Michael S. Tsirkin
2017-05-07 4:22 ` Wang, Wei W [this message]
2017-05-04 8:50 ` [PATCH v10 4/6] mm: function to offer a page block on the free list Wei Wang
2017-05-05 0:21 ` kbuild test robot
2017-05-05 22:12 ` Michael S. Tsirkin
2017-05-04 8:50 ` [PATCH v10 5/6] mm: export symbol of next_zone and first_online_pgdat Wei Wang
2017-05-04 8:50 ` [PATCH v10 6/6] virtio-balloon: VIRTIO_BALLOON_F_MISC_VQ Wei Wang
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