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A Real-Time, Parallel GUI Service in Tesselation OS

A Real-Time, Parallel GUI Service in Tesselation OS. Albert Kim, Juan A. Colmenares , Hilfi Alkaff , and John Kubiatowicz Par Lab, UC Berkeley. Motivation: Responsiveness. Screen freezes because the GUI system has been swapped out Browser’s GUI might disappear when compiling

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A Real-Time, Parallel GUI Service in Tesselation OS

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  1. A Real-Time, Parallel GUI Servicein Tesselation OS Albert Kim, Juan A. Colmenares, HilfiAlkaff, and John Kubiatowicz Par Lab, UC Berkeley

  2. Motivation: Responsiveness • Screen freezes because the GUI system has been swapped out • Browser’s GUI might disappear when compiling • Impossible for me to watch a video while running a simulation We’re going to show how to fix this

  3. Overview • Definition of GUI Service: • Render graphics • Handle image/video processing tasks • Window management • Want some desired features over basic definition • Operate on user-meaningful “actions” • E.g. “draw frame”, “move window” • Service time guarantees (soft real-time) • Differentiated service per application • E.g. text editor vs video • Performance isolation from other applications • Reduce overall service time via task parallelism

  4. Overall Model Draw Frame • GUI Service is performance-isolated entity • Graphics rendering can be offloaded • Can take a global view of GUI actions • Acts as front-end to the framebuffer and input devices

  5. It Works!

  6. Sneak Peek at Data Out of 4000 frames Traditional GUI System GUI Service (1 core) GUI Service (4 cores)

  7. Service Time Guarantees for User Actions • User actions have deadlines (real-time) • Use CPU reservation to allocate CPU time for each application • Each application may request different amounts of CPU reservation • Guaranteed CPU time • No denial-of-service • Custom scheduler that combines: • Global Earliest Deadline First (GEDF) • Multiprocessor Aperiodic Server (MAS) Action 1 Action 2 Action 1 Action 3 CPU Time in GUI Service

  8. Achieving Performance Isolation • GUI Service should not conflict with other apps • Take advantage of Tessellation OS • Tessellation’s goals: • Support a varied mix of applications • Enable applications to deliver guaranteed/consistent performance • Even in scenarios in which applications have conflicting requirements • Basic Idea: Tessellation partitions resources (e.g. cores, cache partitions) Space Time

  9. Performance Isolation (continued) Cell A • Cell: the basic partitioning abstraction • Full control over resources it owns • Encapsulates entire runtime system • Has its own scheduler and memory management system • Efficient inter-cell communication using channels • Space-time partitioning • Resources for cells are gang-scheduled • No uncontrolled virtualization • Two-level scheduling • 1st-level scheduler (Kernel) • 2nd-level scheduler (User) App 1 App 2 Task 2nd-level Mem Mgmt 2nd-level Scheduling Channel Cell B Space Time

  10. Parallelism • Rendering is CPU-intensive, so parallelize • Not a problem for non-overlapping windows • Even for overlapping, we can use virtual framebuffers (VFB) • Render to virtual framebuffer, then use screen region map (SRM) when flushing to the real framebuffer • It gets tricky with window management VFB VFB SRM

  11. GUI Service Architecture

  12. Experiment Setup • Capture end-to-end service times (less is better) • 8 video clients, each sending 4000 video frame requests • 4 are 30-fps videos (352 x 288) • 4 are 60-fps videos (352 x 288) • 5 different GUI system setups • Traditional window system running on Linux (Nano-X/Linux) • Traditional window system running on Tessellation (Nano-X/Tess) • GUI Service running on Tessellation • With 1 core (GuiServ(1)/Tess) • With 2 cores (GuiServ(2)/Tess) • With 4 cores (GuiServ(4)/Tess) • Running on machine with 8 hyperthreads • Window system and video clients running on separate cores

  13. Experimental Data Out of 4000 frames Nano-X/ Linux GuiServ(1)/ Tess Nano-X/ Tess GuiServ(4)/ Tess GuiServ(2)/ Tess

  14. Service Level Agreement EstablishmentOngoing Work • Right now, we have to manually profile applications to figure out how much CPU time they require from the GUI Service • Painful and takes a lot of effort • Reason why people don’t like doing real-time • We can profile applications on-the-fly Visual App (Best Effort) Visual App (Real-Time) GUI Service User Action User Action Probe Request Accept User Action Probe Request CPU Time in GUI Service SLA

  15. Network Service ArchitectureOngoing Work Network Interface Card

  16. Related Work • John E. Sasinowski and Jay K. Strosnider. ARTIFACT: A platform evaluating real-time window system designs. In Proc. of RTSS’95 • Norman Feske and Hermann Hartig. DOpE – a window server for real-time and embedded systems. Technical Report TUD FI03 • Nicola Mainca et al. QoS support in X11 window system. Proc. Of RTAS’08

  17. Final Remarks • GUI Service meets time requirements of clients in situations in which traditional window systems fail to do so • GUI Service meets these requirements by leveraging: • Service time guarantees using real-time schedulers • Performance isolation using Tessellation • Task-level parallelism • GUI Service architecture provides an overall pattern for other QoS-aware services

  18. Thanks!

  19. Acknowledgments • Research supported by • Microsoft (Award #024263) • Intel (Award #024894) • U.C. Discovery funding (Award #DIG07-102270) • Additional support from Par Lab affiliates • National Instruments, NEC, Nokia, NVIDIA, Samsung, and Sun Microsystems.

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