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Towards Unobtrusive VM Live Migration for Cloud Computing Platforms

Towards Unobtrusive VM Live Migration for Cloud Computing Platforms. Akane Koto†, Hiroshi Yamada†, Kei Ohmura * , Kenji Kono † Keio University†, NTT Software Innovation Center*. Cloud Computing. Virtualization technology is widely used in cloud computing platforms

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Towards Unobtrusive VM Live Migration for Cloud Computing Platforms

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  1. Towards Unobtrusive VM Live Migration for Cloud Computing Platforms Akane Koto†, Hiroshi Yamada†, Kei Ohmura*, Kenji Kono† Keio University†, NTT Software Innovation Center*

  2. Cloud Computing • Virtualization technology is widely used in cloud computing platforms • Several virtual machines (VM) coexist on the same physical host • Computing resources can be managed efficiently • Live migration ismore effective at managing computing resources • For load balancing and maintenance of physical machines VMM migrates heavily-loaded VM to another host machine VMM migrates lightly-loaded VMs to another host machine Sudden requestbursts have occurred VM2 VM2 VM3 VM1 VM3 VM1 Host B Host C Host A

  3. Live Migration • Moves a running VM between different physical machines without losing its current states • e.g. network connection • [Clark et al. NSDI’05] • Almost all pages are transferred while VM is running • Only processor pages are transferred after VM is suspended • Pages to which register values are saved Almost all pages are transferred while VM is running VM VM memory page memory page Processor pages are transferred after VM is suspended Source Host Destination Host

  4. Migration Noise • Live migration transfers all the memory pages of a VM • Consumes CPU time and network bandwidth significantly • Live migration causes migration noise • Side effects of live migration • Resource contention with the collocated VMs • Degraded performance of collocated VMs • Increase of total migration time VM2’s performance is degraded during live migration Sudden requestbursts have occurred VM3’s migration time is increased VM2 VM3 request burst VM1 VM3 Host B Host A

  5. Effect of Migration Noise • Objective • Examine how migration noise interferes with collocated VMs • Method • Run two VMs on source host machine • Run a postmark benchmark on each VM • postmark: benchmark modeled after an e-mail server • Change one VM’s workload heavier • Migrate another VM to destination host machine VM1’s workload has become heavier unpredictably Experimental environment (Source/Destination host machine) VMM Xen 4.1.0 CPU Xeon 2.8 GHz (domain U) OS Fedora 14(x86_64) Kernel Linux 2.6.38.8 Memory 2GB Live migration Workload changed VM2 VM1 VM2 Host (Source) Host (Destination)

  6. Result: throughput • Domain Us’ throughput degrades by 30% due to occurrence migration noise during domain U1’s migration

  7. Result: CPU usage • CPU contention occurs at source site during live migration • CPU usage on the destination is high during live migration • Receives transferred pages and sets up data structures for the VM Source Destination

  8. SonicMigration • An approach to mitigating migration noise • Shortens the total execution time of live migration • Reduces CPU usage • Cuts network traffic • SonicMigration prunes the VM memory to reduce the number of pages to be transferred • VM marks some pages that aren’t needed to be sent to destination host SonicMigration prunes VM1’s memory VMM reproduces VM1’s memory pages on demand SonicMigration tempers degradation of VM2’s performance VM2 VM1 VM1 request burst VM1’s total migration time is shortened VMM (Source) VMM (Destination)

  9. Soft page • SonicMigration prunes VM memory by not transferring “soft” pages • Soft pages are able to be reallocated at destination site • e.g. file cache pages, free pages • Sends only hard pages that should be transferred during live migration • e.g. processor pages, dirty pages, locked pages • Soft pages are reproduced or initialized when the VM uses them at destination site Free pages are initialized when the kernel uses them VM VM memory page memory page VMM migrates only hard page VMM (Source) VMM (Destination) VM can reproduce pages by reading the data from disk Hard page Soft page

  10. Design of SonicMigration • Extend the guest kernel to inform the VMM which pages are the soft pages 1. Guest sends its memory status 4. Guest updates its kernel state to indicate it doesn’t have any soft pages Host VM guest VM guest VM memory page 2. Live Migration command sent 6. VMM reallocates some memory pages memory page VMM (Source) Virtual interrupt Shared memory VMM (Destination) Live Migration 3, 5. VMM checks shared memory and migrates only hard page memory Hard page Soft page

  11. Experiments • Objective • Confirm how effectively SonicMigration mitigates migration noise • Make comparison with Xen-based live migration on • total migration time • network traffic • Method • Run one domain U on one machine • Read files on domain U to fill its buffer cache • Run varied workloads on domain U to allocate various amount of pages • Migrate the domain U from source to destination Experimental environment (Source/Destination host machine) VMM Xen 4.1.0 CPU Xeon 2.8 GHz (domain U) OS Fedora 14(x86_64) Memory 2GB Kernel Linux 2.6.38.8

  12. Total migration time • SonicMigration shortens migration time as the hard pagesdecrease in number • The total migration time of the prototype shortened 68.3 % at the most

  13. Network traffic • SonicMigration reduces # of transferred memory pages as the hard pages decrease in number • # of the pages is reduced by 83.9% at most, compared to the original migration mechanism

  14. Related Work • Post-copy based live migration [Hines et al. VEE’09] • Transfers the processor states at first, and copies the memory pages when the VM accesses them • Fails to readily allocate more memory to the heavily loaded VM • Has to retain the memory pages on the source until the transfer of all pages is complete • CR/RT - Motion [Liu et al. HPDC’09] • Sends execution trace logs to the destination and creates the same state VM by replaying execution based on it • Causes migration noise since replaying the execution consumes CPU time • Delta compression live migration [Svärd et al. VEE’11] • Reduces total amount of memory sent by compressing the delta which consists of frequently accessed pages • SonicMigration can be combined with every live migration and mitigates migration noise

  15. Conclusion • Live migration causes migration noise • Side effects of live migration • Migration noise degrades the performance of the collocated VMs • Our solution: SonicMigration • Prunes the VM memory to be transferred by avoiding to send soft pages • Soft pages can be reallocated at destination site • Shortens the total migration time by 68.3 % • Lowers the network usage by 83.9 %

  16. Current Status • Extend SonicMigration to make live migration more unobtrusive • Analyze to find any other soft pages • Adjust how many soft pages SonicMigration discards • The performance of resumed VM can be degraded • The guest kernel cannot access page caches stored on the source • Consider not only the collocated VM’s performance but also that of the migrating VM

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