1 / 24

Our work on virtualization

Our work on virtualization. Chen Haogang, Wang Xiaolin {hchen, wxl}@pku.edu.cn Institute of Network and Information Systems School of Electrical Engineering and Computer Science Peking University 2008.11. Agenda. Work at PKU Remote paging for VM Transparent paravirtualization

bryar-kidd
Télécharger la présentation

Our work on virtualization

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Our work on virtualization Chen Haogang, Wang Xiaolin {hchen, wxl}@pku.edu.cn Institute of Network and Information Systems School of Electrical Engineering and Computer SciencePeking University 2008.11

  2. Agenda • Work at PKU • Remote paging for VM • Transparent paravirtualization • Virtual resource sharing • Cache management in Multi-Core and Virtualization environment http://ncis.pku.edu.cn

  3. REMOCA: Hypervisor Remote Disk Cache • Motivation • To improve paging performance for memory-intensive or I/O-intensive workloads by utilizing free memory resource on another physical machine • Solution • The remote memory plays the role of a storage cache between a VM’s virtual memory and its virtual disk devices. • In most cases, the network latency is much lower than the disk latency (1~2 magnitude) http://ncis.pku.edu.cn

  4. REMOCA: The design of REMOCA • Local Module: a ghost buffer • REMOCA is an exclusive cache • Remote Module: the memory service http://ncis.pku.edu.cn

  5. Summary of REMOCA • REMOCA can efficiently alleviate the impact of thrashing behavior, and also significantly improve the performance for real-world I/O intensive applications. • Future work • Cluster-wide memory balancing • Predicting miss ratio before allocating Remote cache size: 768MB http://ncis.pku.edu.cn

  6. 主要内容 • Work at PKU • Remote paging for VM • Transparent paravirtualization • Virtual resource sharing • Cache management in Multi-Core and Virtualization environment http://ncis.pku.edu.cn

  7. Transparent paravirtualization • Some limitation of current hardware-assistant virtualization • Too many VMexits incur significant overhead. • Most VM exits are related to page fault or I/O operation Reason and count of VM exits http://ncis.pku.edu.cn

  8. Top 10 trap instructions with high VM exits frequency in KVM-54 (io: I/O operation, pf: page fault, rd cr: read control registers, clts and hlt: x86 instructions, ot: others) http://ncis.pku.edu.cn

  9. Hot Instructions detection and translation • How to reduce VM exits • Paravirtualization • Xenand KVMapply paravirtualization to improve performance. • The needs to change the source code damages its applicability. • Transparent paravirtualization • Detecting Hot Instructions • An efficient mechanism to catch 97% with top 64 instructions • Replacing Hot Instructions • New or even complex assistant mechanisms should be introduced into VMM to make the replacement safe and possible • Implanting Replaced Instructions to Guest OS • Adaptive code implantation http://ncis.pku.edu.cn

  10. Implementation in KVM http://ncis.pku.edu.cn

  11. Transparent Memory Paravirtualization • A New Memory Virtualization Mechanism • Transfers the guest OS page table to map guest virtual addresses directly to host physical addresses. • The transferred guest page table, called direct page table, is directly registered with the hardware MMU. • A process using direct page table is called as a para-virtualized process. • To provide the guest OS an independent view of its own physical address space as used for guest OS memory management. • When the guest OS accesses the direct page table, it expects guest physical addresses rather than host physical addresses as currently presented in the direct page table. http://ncis.pku.edu.cn

  12. Transparent Memory Paravirtualization The Direct page table structure of A New Memory Virtualization Mechanism http://ncis.pku.edu.cn

  13. Evaluation http://ncis.pku.edu.cn

  14. Evaluation http://ncis.pku.edu.cn

  15. Transparent Paravirtualization • Future work • TMP Evaluation • Impact on cache hits • Compares with: EPT/NPT，Shadow Page Table • Compares with: KVM Para-MMU，Xen Para-MMU • Transparent MMU Extension • Linux  Windows • Emulate all Guest OS page faults • TMP  Transparent Para-IO • Other hot instructions • Limitation of Transparent Paravirtualization • Security vs. performance http://ncis.pku.edu.cn

  16. Agenda • Work at PKU • Remote paging for VM • Transparent paravirtualization • Virtual resource sharing • Cache management in Multi-Core and Virtualization environment http://ncis.pku.edu.cn

  17. Virtual resource sharing • Motivation • In a homogeneous environment, how to achieve high-degree of resource sharing while preserving isolation? • Example: Network classroom @ PKU Zhongzhi • Teaching Windows, MS Office or VC++ programming • About 30 students per class • Homogeneous OS, software,data and application instances http://ncis.pku.edu.cn

  18. Virtual resource sharing • Limitations of current solutions • Terminal server: bad isolation • Preferred to run a single OS per student • VM live clone: cannot provide data persistency • Content-based sharing: high scanning overhead • Difference Engine (OSDI ’08): unable to share during OS startup or application startup • Goal • Fast startup of VMs and applications • Accurate resource sharing • Low management overhead

  19. Virtual resource sharing • Solution: a bottom-up approach • Starts from disk sharing • Map identical disk blocks to a single storage location • Manage a shared disk cache within the VMM • Replace disk reads with page remapping • Fast application startup • Challenges • How to discover identical disk blocks? • CoW disk / CAS • How to handle sharable application data, especially the “zero pages”?

  20. Agenda • Work at PKU • Remote paging for VM • Transparent para-virtualization • Virtual resource sharing • Cache management in Multi-Core and Virtualization environment http://ncis.pku.edu.cn

  21. Cache management in Multi-Core • Motivation • Current VMM cannot make efficient use of the cache hierarchy in a multi-core platform • Objectives • Explore new compiling and profiling techniques to analyze and predict memory access behavior of a program • Implement the cache-aware memory allocation and CPU scheduling in the VMM • Dynamic memory balancing among VMs http://ncis.pku.edu.cn

  22. Cache management in Multi-Core • Lower-level cache partitioning • Avoid cache contention for concurrent VMs • Using page-coloring technique • Restricting the number of cache sets that a VM can use • Transparent to the guest OS http://ncis.pku.edu.cn

  23. Cache management in Multi-Core • Challenges • Predicting the performance impact to the application before partitioning • Online profiling and dynamic re-partitioning • Reducing page migration overhead • Cooperating with VM scheduling, especially CPU allocation and migration • New micro-architectures • Example: Intel Nehalem256 KB dedicated L2 per core and shared L3 http://ncis.pku.edu.cn

  24. Thanks！ Q&A Discussion

More Related