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SubjectRe: [virtio-dev] [RFC for Linux v4 0/2] virtio_balloon: Add VIRTIO_BALLOON_F_CONT_PAGES to report continuous pages
On Thu, Jul 16, 2020 at 03:01:18PM +0800, teawater wrote:
>
>
> > 2020年7月16日 14:38,Michael S. Tsirkin <mst@redhat.com> 写道:
> >
> > On Thu, Jul 16, 2020 at 10:41:50AM +0800, Hui Zhu wrote:
> >> The first, second and third version are in [1], [2] and [3].
> >> Code of current version for Linux and qemu is available in [4] and [5].
> >> Update of this version:
> >> 1. Report continuous pages will increase the speed. So added deflate
> >> continuous pages.
> >> 2. According to the comments from David in [6], added 2 new vqs inflate_cont_vq
> >> and deflate_cont_vq to report continuous pages with format 32 bits pfn and 32
> >> bits size.
> >> Following is the introduction of the function.
> >> These patches add VIRTIO_BALLOON_F_CONT_PAGES to virtio_balloon. With this
> >> flag, balloon tries to use continuous pages to inflate and deflate.
> >> Opening this flag can bring two benefits:
> >> 1. Report continuous pages will increase memory report size of each time
> >> call tell_host. Then it will increase the speed of balloon inflate and
> >> deflate.
> >> 2. Host THPs will be splitted when qemu release the page of balloon inflate.
> >> Inflate balloon with continuous pages will let QEMU release the pages
> >> of same THPs. That will help decrease the splitted THPs number in
> >> the host.
> >> Following is an example in a VM with 1G memory 1CPU. This test setups an
> >> environment that has a lot of fragmentation pages. Then inflate balloon will
> >> split the THPs.
>
>
> >> // This is the THP number before VM execution in the host.
> >> // None use THP.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 0 kB
> These lines are from host.
>
> >> // After VM start, use usemem
> >> // (https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git)
> >> // punch-holes function generates 400m fragmentation pages in the guest
> >> // kernel.
> >> usemem --punch-holes -s -1 800m &
> These lines are from guest. They setups the environment that has a lot of fragmentation pages.
>
> >> // This is the THP number after this command in the host.
> >> // Some THP is used by VM because usemem will access 800M memory
> >> // in the guest.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 911360 kB
> These lines are from host.
>
> >> // Connect to the QEMU monitor, setup balloon, and set it size to 600M.
> >> (qemu) device_add virtio-balloon-pci,id=balloon1
> >> (qemu) info balloon
> >> balloon: actual=1024
> >> (qemu) balloon 600
> >> (qemu) info balloon
> >> balloon: actual=600
> These lines are from host.
>
> >> // This is the THP number after inflate the balloon in the host.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 88064 kB
> These lines are from host.
>
> >> // Set the size back to 1024M in the QEMU monitor.
> >> (qemu) balloon 1024
> >> (qemu) info balloon
> >> balloon: actual=1024
> These lines are from host.
>
> >> // Use usemem to increase the memory usage of QEMU.
> >> killall usemem
> >> usemem 800m
> These lines are from guest.
>
> >> // This is the THP number after this operation.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 65536 kB
> These lines are from host.
>
>
>
> >>
> >> Following example change to use continuous pages balloon. The number of
> >> splitted THPs is decreased.
> >> // This is the THP number before VM execution in the host.
> >> // None use THP.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 0 kB
> These lines are from host.
>
> >> // After VM start, use usemem punch-holes function generates 400M
> >> // fragmentation pages in the guest kernel.
> >> usemem --punch-holes -s -1 800m &
> These lines are from guest. They setups the environment that has a lot of fragmentation pages.
>
> >> // This is the THP number after this command in the host.
> >> // Some THP is used by VM because usemem will access 800M memory
> >> // in the guest.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 911360 kB
> These lines are from host.
>
> >> // Connect to the QEMU monitor, setup balloon, and set it size to 600M.
> >> (qemu) device_add virtio-balloon-pci,id=balloon1,cont-pages=on
> >> (qemu) info balloon
> >> balloon: actual=1024
> >> (qemu) balloon 600
> >> (qemu) info balloon
> >> balloon: actual=600
> These lines are from host.
>
> >> // This is the THP number after inflate the balloon in the host.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 616448 kB
> >> // Set the size back to 1024M in the QEMU monitor.
> >> (qemu) balloon 1024
> >> (qemu) info balloon
> >> balloon: actual=1024
> These lines are from host.
>
> >> // Use usemem to increase the memory usage of QEMU.
> >> killall usemem
> >> usemem 800m
> These lines are from guest.
>
> >> // This is the THP number after this operation.
> >> cat /proc/meminfo | grep AnonHugePages:
> >> AnonHugePages: 907264 kB
> These lines are from host.
>
> >
> > I'm a bit confused about which of the above run within guest,
> > and which run within host. Could you explain pls?
> >
> >
>
> I added some introduction to show where these lines is get from.
>
> Best,
> Hui


OK so we see host has more free THPs. But guest has presumably less now - so
the total page table depth is the same. Did we gain anything?

>
> >
> >> [1] https://lkml.org/lkml/2020/3/12/144
> >> [2] https://lore.kernel.org/linux-mm/1584893097-12317-1-git-send-email-teawater@gmail.com/
> >> [3] https://lkml.org/lkml/2020/5/12/324
> >> [4] https://github.com/teawater/linux/tree/balloon_conts
> >> [5] https://github.com/teawater/qemu/tree/balloon_conts
> >> [6] https://lkml.org/lkml/2020/5/13/1211
> >>
> >> Hui Zhu (2):
> >> virtio_balloon: Add VIRTIO_BALLOON_F_CONT_PAGES and inflate_cont_vq
> >> virtio_balloon: Add deflate_cont_vq to deflate continuous pages
> >>
> >> drivers/virtio/virtio_balloon.c | 180 +++++++++++++++++++++++++++++++-----
> >> include/linux/balloon_compaction.h | 12 ++
> >> include/uapi/linux/virtio_balloon.h | 1
> >> mm/balloon_compaction.c | 117 +++++++++++++++++++++--
> >> 4 files changed, 280 insertions(+), 30 deletions(-)
> >
> >
> > ---------------------------------------------------------------------
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> > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org

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