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SubjectRe: [RFC for Linux v4 0/2] virtio_balloon: Add VIRTIO_BALLOON_F_CONT_PAGES to report continuous pages
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
> // 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 &
> // 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
> // 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
> // This is the THP number after inflate the balloon in the host.
> cat /proc/meminfo | grep AnonHugePages:
> AnonHugePages: 88064 kB
> // Set the size back to 1024M in the QEMU monitor.
> (qemu) balloon 1024
> (qemu) info balloon
> balloon: actual=1024
> // Use usemem to increase the memory usage of QEMU.
> killall usemem
> usemem 800m
> // This is the THP number after this operation.
> cat /proc/meminfo | grep AnonHugePages:
> AnonHugePages: 65536 kB
>
> 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
> // After VM start, use usemem punch-holes function generates 400M
> // fragmentation pages in the guest kernel.
> usemem --punch-holes -s -1 800m &
> // 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
> // 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
> // 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
> // Use usemem to increase the memory usage of QEMU.
> killall usemem
> usemem 800m
> // This is the THP number after this operation.
> cat /proc/meminfo | grep AnonHugePages:
> AnonHugePages: 907264 kB

I'm a bit confused about which of the above run within guest,
and which run within host. Could you explain pls?



> [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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