Messages in this thread | | | Date | Sat, 30 Jun 2018 12:31:19 +0800 | From | Wei Wang <> | Subject | Re: [PATCH v34 0/4] Virtio-balloon: support free page reporting |
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On 06/25/2018 08:05 PM, 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 = 284ms vs 1757ms --> ~84% reduction
According to Michael's comments, add one more set of data here:
Enabling page poison with value=0, and enable KSM.
The legacy live migration time is 1806ms (averaged across 10 runs), compared to the case with this optimization feature in use (i.e. 284ms), there is still around ~84% reduction.
Best, Wei
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