Boosting GPU Virtualization Performance with Hybrid Shadow Page Tables

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1 Boosting GPU Virtualization Performance with Hybrid Shadow Page Tables Yaozu Dong Mochi Xue Xiao Zheng Jiajun Wang Zhengwei Qi Haibing Guan Shanghai Jiao Tong University Intel Corporation

2 GPU Usage Gaming (2D/3D graphic) HD video hardware decoding High performance computing High Performance Computing shifts computation- intensive workloads to cloud environment. Machine learning Molecular dynamics simulations Media transcoding A new computing paradigm: GPU Cloud

3 ghyvi An optimized GPU virtualization scheme based on gvirt. GMedia: A media transcoding benchmark Relaxed Shadow Page Table Adaptive Hybrid Page Table Shadowing Policies Up to 13x performance of gvirt and 85% of native.

4 GPU benchmarks 2D/3D graphic For OpenGL and DirectX commands Such as 3DMark, PassMark GPGPU For CUDA and OpenCL commands Such as Rodinia [ATC2013], Parboil

MSDK provides APIs for hardware acceleration.

5 GMedia A hardware media transcoding benchmark based on Intel s MSDK(Media Software Development Kit). MSDK provides APIs for hardware acceleration. A wrapper invokes media functions form MSDK. Test cases can run with assigned threads and settings. The FPS results reflect the performance.

Massive update issue 1000 900 800 700 600

480p 24, 480p 25, 480p 30, 480p Native gvirt

500 450 400 350 300 250 200 150 100 50 0 1,

Native gvirt 250 200 150 100 50 0 1, 1080p

6 Massive update issue , 480p 10, 480p 20, 480p 24, 480p 25, 480p 30, 480p Native gvirt NATIVE GVIRT 93% performance degrade , 720p 5, 720p 10, 720p 15, 720p 20, 720p Native gvirt , 1080p 4, 1080p 5, 1080p 6, 1080p 7, 1080p 10, 1080p Native gvirt

7 Shadow page table Page Directory Table Page Table Guest Host PDE PDE PTE PTE System memory Shadow Page Directory Table Shadow Page Table 512 * 1024 * 4KB = 2GB Resource partition User space isolation

8 Strict shadow page table Trap- and- emulation Write protect the page table Page fault happens Update shadow page table Page table gvirt Shadow page table

9 Case profiling Proportion changes 21.43% 79.45%

10 Breakdown of EPT_VIOLATION Take 15thread- 720p as an example: 62% of all VM_exit is due to EPT_VIOLATION 83% of EPT_VIOLATIONis caused bypte access 62% EPT_VIOLATION 83% PTE_ACCESS

11 Frequency The frequency of update in 10s. Up to 7.5k times

12 Hot page tables Hot page tables

13 Continuous updates Same table

14 Conclusion of massive update issue VM is frequently swapping graphic memorypages. It modifies the entries of page table massively. Large amount of updates(7.5k in 10s) Updates focus on certain pages (hot pages) Updates are continuous (on the same page) Modificationslead to busytrap- and- emulations. Eventually, overhead happens. (Up to 95%)

15 ghyvi architecture gvirt Host VM Native GFX Driver Page Table Guest VM Native GFX Driver Page Table ghyvi Strict SPT Relaxed SPT VMM GPU Hyper call Pass Through Trap

16 GPU programming model tail CPU head GPU The commands fed by CPU won t take effect until they are fetched by the GPU.

17 Relaxed shadow page table Remove write protection Page table ghyvi Shadow page table

18 Relaxed shadow page table Page table ghyvi Shadow page table

19 Relaxed shadow page table Page table Reconstruct ghyvi Shadow page table

20 Page table reconstruction Step1: Take a snapshot of guest page table Page table Guest Host Strict shadow page table Snapshot

21 Page table reconstruction Step2: Massive update Page table Guest Host Strict shadow page table Snapshot

22 Page table reconstruction Step3: Compare with snapshot Page table Guest Host Relaxed shadow page table Snapshot

23 Page table reconstruction Step 4: Reconstruct the different part Page table Guest Host Relaxed shadow page table Snapshot

24 Hybrid page table shadowing Dynamic Segmented partial relaxed Full relaxed Dynamic partial relaxed Static partial relaxed 4 Policies for Performance Tuning

25 Static partial relaxed Select 50, 100, 200, 300 hot pages Switch them into relaxed mode

26 Dynamic partial relaxed All the pages are in strict mode at first Switch to relaxed mode once it s touched

27 Dynamic segmented partial relaxed All the pages are in strict mode at first Switch to relaxed mode once it s touched Reset the relaxed pages after reconstruction

28 Evaluation 4 policies of page table shadowing Full reconstruction Static partial reconstruction Dynamic partial reconstruction Dynamic segmented partial reconstruction Linux 2D/3D performance Windows 2D/3D performance

29 Configuration CPU RAM HDD GPU 4th Intel Haswell i5 (2.4Ghz) 8GB Hardware Seagate 500GB Intel Processor Graphics With 2GB global graphics memory Software Linux VM 64bit Ubuntu Windows VM 64bit Windows 7 Xen 4.3 VM configuration 4 VCPUS and 2GB system memory

Evaluation: full relaxed 900 800 700 600 500 400

25, 480p 30, 480p gvirt Full The performance of

The performance of issue cases are improved.

720p 10, 720p 15, 720p 20, 720p gvirt Full 200

30 Evaluation: full relaxed , 480p 10, 480p 20, 480p 24, 480p 25, 480p 30, 480p gvirt Full The performance of normal cases are degraded. The performance of issue cases are improved , 720p 5, 720p 10, 720p 15, 720p 20, 720p gvirt Full , 1080p 4, 1080p 5, 1080p 6, 1080p 7, 1080p 10, 1080p gvirt Full

Evaluation: static partial relaxed The performance of normal cases becomes worse with more relaxed pages. The performance of issue cases are improved.

31 Evaluation: static partial relaxed The performance of normal cases becomes worse with more relaxed pages. The performance of issue cases are improved. The coverage of hot pages affects the performance , 480p 10, 480p 20, 480p 24, 480p 25, 480p 30, 480p Native gvirt Static Partial 50 Static Partial 100 Static Partial 200 Static Partial 300

Evaluation: dynamic relaxed 1000 800 600 400 Dynamic segmented partial works fine

200 0 1, 480p 10, 480p 20, 480p 24, 480p 25, 480p 30, 480p Native gvirt Dynamic

300 150 200 100 100 50 0 1, 720p 5, 720p 10, 720p 15, 720p 20, 720p 0 1, 1080p 4,

32 Evaluation: dynamic relaxed Dynamic segmented partial works fine on normal cases , 480p 10, 480p 20, 480p 24, 480p 25, 480p 30, 480p Native gvirt Dynamic Partial Dynamic Segmented Partial Up to 13x of gvirt 85% of native , 720p 5, 720p 10, 720p 15, 720p 20, 720p 0 1, 1080p 4, 1080p 5, 1080p 6, 1080p 7, 1080p 10, 1080p Native gvirt Dynamic Partial Dynamic Segmented Partial Native gvirt Dynamic Partial Dynamic Segmented Partial

Linux 2D/3D performance Slightly better than gvirt. 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.

33 Linux 2D/3D performance Slightly better than gvirt firefox- scrolling firefox- asteroids midori- zoomed gnome- system- moitor lightsmark xonotic openarena urbanterror gvirt ghyvi

34 Windows 2D/3D performance Discrepancy is acceptable SM2.0 HDR/SM3.0 Pass2D #"Heaven fps" Heaven gvirt ghyvi

35 Summary An optimized GPU virtualization scheme based on gvirt. New shadow page table: relaxed shadow page table Adaptive hybrid page table shadowing policies Up to 13x performance improvement. Source code is available g

36 Q&A Boosting GPU Virtualization Performance with Hybrid Shadow Page Tables

Boosting GPU Virtualization Performance with Hybrid Shadow Page Tables

Boosting GPU Virtualization Performance with Hybrid Shadow s Yaozu Dong and Mochi Xue, Shanghai Jiao Tong University and Intel Corporation; Xiao Zheng, Intel Corporation; Jiajun Wang, Shanghai Jiao Tong