On Fri, Jul 20, 2018 at 04:33:00PM +0800, Wei Wang wrote: > This patch series is separated from the previous "Virtio-balloon > Enhancement" series. The new feature, VIRTIO_BALLOON_F_FREE_PAGE_HINT, > implemented by this series enables the virtio-balloon driver to report > hints of guest free pages to the host. It can be used to accelerate live > migration of VMs. Here is an introduction of this usage: > > Live migration needs to transfer the VM's memory from the source machine > to the destination round by round. For the 1st round, all the VM's memory > is transferred. From the 2nd round, only the pieces of memory that were > written by the guest (after the 1st round) are transferred. One method > that is popularly used by the hypervisor to track which part of memory is > written is to write-protect all the guest memory. > > This feature enables the optimization by skipping the transfer of guest > free pages during VM live migration. It is not concerned that the memory > pages are used after they are given to the hypervisor as a hint of the > free pages, because they will be tracked by the hypervisor and transferred > in the subsequent round if they are used and written. > > * Tests > - Test Environment > Host: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz > Guest: 8G RAM, 4 vCPU > Migration setup: migrate_set_speed 100G, migrate_set_downtime 2 second > > - Test Results > - Idle Guest Live Migration Time (results are averaged over 10 runs): > - Optimization v.s. Legacy = 409ms vs 1757ms --> ~77% reduction > (setting page poisoning zero and enabling ksm don't affect the > comparison result) > - Guest with Linux Compilation Workload (make bzImage -j4): > - Live Migration Time (average) > Optimization v.s. Legacy = 1407ms v.s. 2528ms --> ~44% reduction > - Linux Compilation Time > Optimization v.s. Legacy = 5min4s v.s. 5min12s > --> no obvious difference I'd like to see dgilbert's take on whether this kind of gain justifies adding a PV interfaces, and what kind of guest workload is appropriate. Cc'd. > ChangeLog: > v35->v36: > - remove the mm patch, as Linus has a suggestion to get free page > addresses via allocation, instead of reading from the free page > list. > - virtio-balloon: > - replace oom notifier with shrinker; > - the guest to host communication interface remains the same as > v32. > - allocate free page blocks and send to host one by one, and free > them after sending all the pages. > > For ChangeLogs from v22 to v35, please reference > https://lwn.net/Articles/759413/ > > For ChangeLogs before v21, please reference > https://lwn.net/Articles/743660/ > > Wei Wang (5): > virtio-balloon: remove BUG() in init_vqs > virtio_balloon: replace oom notifier with shrinker > virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT > mm/page_poison: expose page_poisoning_enabled to kernel modules > virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON > > drivers/virtio/virtio_balloon.c | 456 ++++++++++++++++++++++++++++++------ > include/uapi/linux/virtio_balloon.h | 7 + > mm/page_poison.c | 6 + > 3 files changed, 394 insertions(+), 75 deletions(-) > > -- > 2.7.4
