Re: [virtio-dev] [RFC for Linux v4 0/2] virtio_balloon: Add VIRTIO_BALLOON_F_CONT_PAGES to report continuous pages

[teawater]

> 2020å7æ16æ 14:38ïMichael S. Tsirkin <mst@xxxxxxxxxx> åéï
> 
> 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


> 
>> [1] https://lkml.org/lkml/2020/3/12/144
>> [2] https://lore.kernel.org/linux-mm/1584893097-12317-1-git-send-email-teawater@xxxxxxxxx/
>> [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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