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Ts 3742

  1. 1. 2006 JavaOneSM Conference | Session TS-3742 | Dancing While Gaming— Multitasking VMs (MVM) on Real Devices Jae Hyou Lee Yaniv Shani Samsung Electronics Sun Microsystems, Inc. www.samsung.com www.sun.com TS-3742
  2. 2. 2006 JavaOneSM Conference | Session TS-3742 | 2 Goal Deeper understanding of Multitasking VM implementation on real devices
  3. 3. 2006 JavaOneSM Conference | Session TS-3742 | 3 Project Highlights • A joint collaboration between Samsung Electronics and Sun Microsystems • MVM deployment is based on Sun’s JWC1.1.3 • Deploying most of the MSA JSRs • Tested with hundreds of games and applications from leading content providers
  4. 4. 2006 JavaOneSM Conference | Session TS-3742 | 4 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  5. 5. 2006 JavaOneSM Conference | Session TS-3742 | 5 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  6. 6. 2006 JavaOneSM Conference | Session TS-3742 | 6 What Is MVM? • Running multiple applications simultaneously • Java is always on • Favorite applications instantly available MP3 Playing Chatting Gaming
  7. 7. 2006 JavaOneSM Conference | Session TS-3742 | 7 MVM Conceptual View Device H/W Operating System Native JVM Task Configuration Level MVM Resource Manager App. Manager AMS JSR JSR JSRJSR Profile Level Multitasking Safety Isolation Model Deployment Guidelines Legacy Content New App States User Experience Resource Policies
  8. 8. 2006 JavaOneSM Conference | Session TS-3742 | 8 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  9. 9. 2006 JavaOneSM Conference | Session TS-3742 | 9 Isolates and Tasks Each application runs in its own logical Java Virtual Machine, called an Isolate. Within the JVM, each isolate is represented as a Task. A task consists of one more Java thread of execution.
  10. 10. 2006 JavaOneSM Conference | Session TS-3742 | 10 More on Tasks… • All tasks execute in the same single OS task context • All tasks share: • Constant data structure • Runtime support functions • Each task encapsulates non-sharable program state MVM
  11. 11. 2006 JavaOneSM Conference | Session TS-3742 | 11 Implementation Details • Each task has a separate, private copy of the static variables of all the loaded Java classes • Static variables are only global to all threads within a particular task Static Variable class A { public static int count; ... } Task 1 class A { public static int count; ... } task 2 MVM • Each task maintains a private copy of ‘count’ • The Class representation is shared
  12. 12. 2006 JavaOneSM Conference | Session TS-3742 | 12 Implementation Details Synchronization class A { public static synchronized int open(); } • Synchronization has to be task private • Threads in one task cannot block threads in another task Task 1 Task 2 MVM A.open() A.open() A.open() A.open() Blocking Threads Across Tasks Isn’t Allowed
  13. 13. 2006 JavaOneSM Conference | Session TS-3742 | 13 Resource Management • The JVM is responsible for CPU time and memory resources in order to ensure that all tasks get their “fair” share • Other resources, such as network bandwidth and communication ports are managed by the profile layer
  14. 14. 2006 JavaOneSM Conference | Session TS-3742 | 14 Resource Management—Scheduling • Tasks and thread are scheduled by the JVM • Fair scheduling algorithm is used for task scheduling in order to prevent one task from taking disproportionate CPU time • The ‘Isolate’ class offers a set of APIs to modify the priority levels for each task ` Task 2 Scheduler MVM Task 1 Active Thread MVM
  15. 15. 2006 JavaOneSM Conference | Session TS-3742 | 15 Resource Management—Memory • All tasks allocations are conducted from the same global heap region • The virtual machine has a bookkeeping mechanism that accounts for each task total heap memory consumption • The JVM injects OutOfMemoryError as needed to inform tasks that heap space has become scarce
  16. 16. 2006 JavaOneSM Conference | Session TS-3742 | 16 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  17. 17. 2006 JavaOneSM Conference | Session TS-3742 | 17 New MIDlet State in MVM • An application is said to be in the Foreground when: • Its displayable controls the display • It handles event from the user input mechanism • Only one MIDlet can execute in the Foreground at a time Foreground MIDlet
  18. 18. 2006 JavaOneSM Conference | Session TS-3742 | 18 New MIDlet State in MVM Background MIDlet • An application is in the Background when: • Its displayable does not control the display • It does not handle the user inputs mechanism • Zero or more MIDlets can execute in the Background at a time
  19. 19. 2006 JavaOneSM Conference | Session TS-3742 | 19 The Application Manager • A resident MIDIet • Executed from power on • Lists the running applications • A fast way to switch between running MIDlets • Display background MIDIets alerts
  20. 20. 2006 JavaOneSM Conference | Session TS-3742 | 20 Switching a MIDlet to the Background (1/3) • Upon a short ‘Hot’ key press the foreground MIDlet will be placed in the background and main device menu will be displayed Short ‘Hot’ Key Press Short ‘Hot’ Key
  21. 21. 2006 JavaOneSM Conference | Session TS-3742 | 21 Switching a MIDlet to the Background (2/3) • Upon a long ‘Hot’ key press the foreground MIDlet will be placed in the background and the ‘Application manager’ dialog will be displayed Long ‘Hot’ Key Long ‘Hot’ Key
  22. 22. 2006 JavaOneSM Conference | Session TS-3742 | 22 Switching a MIDlet to the Background (3/3) Invoking Display.setCurrent(null) • Upon calling setCurrent(null) the MIDlet will be placed in the background and the ‘idle’ screen of the device will be displayed Display.setCurrent(null)
  23. 23. 2006 JavaOneSM Conference | Session TS-3742 | 23 Interrupting the User • Background MIDlet calls Display.setCurrent(alert) • Background MIDlet tries to access a protected API and a security dialog is prompted • Noteworthy event occurred in the background • e.g., Incoming IM while playing a game
  24. 24. 2006 JavaOneSM Conference | Session TS-3742 | 24 DEMO User Experience Demonstration
  25. 25. 2006 JavaOneSM Conference | Session TS-3742 | 25 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  26. 26. 2006 JavaOneSM Conference | Session TS-3742 | 26 Managing Resources • In a single-tasking environment, the MIDlet has access to all of the available resources • In a multitasking environment, MIDlets have to compete for available resources
  27. 27. 2006 JavaOneSM Conference | Session TS-3742 | 27 Managing Resources • Mechanisms • Reservation • Quota • Revocation • Policies • Fixed partition • Open for competition • Special cases
  28. 28. 2006 JavaOneSM Conference | Session TS-3742 | 28 Resource Management Mechanisms • A reservation mechanism sets aside a certain amount of a resource for a MIDlet and keeps it available for that MIDlet and that MIDlet alone Reservation
  29. 29. 2006 JavaOneSM Conference | Session TS-3742 | 29 Resource Management Mechanisms • A quota mechanism permits a MIDlet to allocate up to a certain amount of a resource; if the MIDlet attempts to allocate more resources than its quota, the attempt fails, even if resources are actually available on the system Quota
  30. 30. 2006 JavaOneSM Conference | Session TS-3742 | 30 Resource Management Mechanisms • The system can revoke a resource from a MIDlet and give it to another MIDlet • Resource revocation examples: • CPU cycles • Display access • Audio playback • Resource revocation doesn’t always have a dramatic effect on the MIDlet’s execution Revocation
  31. 31. 2006 JavaOneSM Conference | Session TS-3742 | 31 Resource Management Policies • Initial amount of resources are reserved before MIDlet launch • Resource availability validation during MIDlet’s startup • Ensure consistent MIDlet behavior Fixed Partition
  32. 32. 2006 JavaOneSM Conference | Session TS-3742 | 32 Resource Management Policies • No reservation • Resource are acquired and reclaimed at runtime • May lead to unpredictable behavior Open for Competition
  33. 33. 2006 JavaOneSM Conference | Session TS-3742 | 33 Special Resource Management Policies • Only the Foreground can access the LCD display and receive key inputs events • The current displayable of a Background MIDlet is still updated Note: vibrate() ,flashBacklight() and tone playing aren’t honored when invoked from a Background MIDlet LCD Display
  34. 34. 2006 JavaOneSM Conference | Session TS-3742 | 34 Sound (1/2) Special Resource Management Policies • Foreground MIDlets are assigned physical player that can access the audio device resource • Background MIDlets are assigned a logical player that only maintains the audio state • Upon foreground switch the player state is changed automatically Logical Player Physical Player 1 Logical Player Physical Player 2 Foreground Switch
  35. 35. 2006 JavaOneSM Conference | Session TS-3742 | 35 Special Resource Management Policies • Unique JAD file property to lock audio resources • Allows a background MIDlet to be audible • Useful for media players (e.g., the MP3 player, radio, etc.) Sound (2/2) 1 Logical Player Physical Player 2 Logical Player Physical Player 1 Foreground Switch
  36. 36. 2006 JavaOneSM Conference | Session TS-3742 | 36 A Full Resource Policy Matrix Fixed Open Special Memory X X CPU X X File Descriptor X X Socket X X Display X Sound X X Bluetooth X Location X PIM X
  37. 37. 2006 JavaOneSM Conference | Session TS-3742 | 37 Guidelines for Resource Policy Selection • Resource policy definition relies on the underlying platform capabilities and requirements • Fixed partition policy should be used for fundamental resources that are required by the majority of the applications (e.g., memory, file, socket) • Open policy should be used resources that are used by specific MIDlets and have limited availability (e.g., Bluetooth, location) • Display and sound requires special handling
  38. 38. 2006 JavaOneSM Conference | Session TS-3742 | 38 DEMO Resource Policy Demonstration
  39. 39. 2006 JavaOneSM Conference | Session TS-3742 | 39 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  40. 40. 2006 JavaOneSM Conference | Session TS-3742 | 40 Multitasking Safety • The native JVM task can run native code for any task, hence the code must be made aware of the task on whose behalf it is being called and possibly allocating resources • When the task context is established, the code is considered multitasking safe • Sun’s JWC software is multitasking safe
  41. 41. 2006 JavaOneSM Conference | Session TS-3742 | 41 Multitasking Safety Implementation Guidelines • In some cases a deployment of a profile to MVM environment requires additional development in order that the profile will execute properly Foreground Switch Blocking Threads Across Tasks Isn’t Allowed
  42. 42. 2006 JavaOneSM Conference | Session TS-3742 | 42 Multitasking Safety • At Java level, each task has a separate, private copy of the static variables of all the loaded Java classes • This is handled internally by the MVM • Native code often has global data • Native data is shared across all tasks! • Global native data needs to be replicated for each task • Held as a field of a Java object • Proper handling for singleton depends on whether it is meant be used on a per-task basis (the default behavior for MVM), or by the entire system Static and Global Variable
  43. 43. 2006 JavaOneSM Conference | Session TS-3742 | 43 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  44. 44. 2006 JavaOneSM Conference | Session TS-3742 | 44 MIDlet Guidelines • MIDlets developed on top of ‘Canvas’ class will receive the following notifications: • Canvas.hideNotify(): When switching to background • Canvas.showNotify(): When returning to foreground • MIDP2.0 spec. doesn’t offer APIs for MIDlet that doesn’t use the ‘Canvas’ class facilities MIDlet State Detection
  45. 45. 2006 JavaOneSM Conference | Session TS-3742 | 45 MIDlet Guidelines • Switching to background does not pause a MIDlet by default • Legacy content handling • Some MIDlets (e.g., legacy games) will not run correctly in the background • A new JADfile property can request that the MIDlet be paused when switched to background In the Background, Am I Paused?
  46. 46. 2006 JavaOneSM Conference | Session TS-3742 | 46 MIDlet State Detection • Most of the games should be suspended in background • Player may be inadvertently killed • Free up resource that aren’t in use • No need to continue painting when nobody sees the results • Make sure to attract the users attention when something interesting happens in the background How to Behave While Executing in Background?
  47. 47. 2006 JavaOneSM Conference | Session TS-3742 | 47 MIDlet Guidelines • Return resources when you are done with them, don’t wait for destroyApp() • Expect and detect failures in resource acquisition • Help the users to overcome resource acquisition failure • Expect to see new JAD file properties for resource policy indication (heap size, special sound policy, etc.) Resource Awareness
  48. 48. 2006 JavaOneSM Conference | Session TS-3742 | 48 Boot-time MIDlets • Launch in the background at boot time • Bring to foreground upon arrival of incoming event • Examples: • MMS, SMS, IM, Mail clients • Stock, weather, news
  49. 49. 2006 JavaOneSM Conference | Session TS-3742 | 49 Summary • MVM in the configuration level: • Isolation Model • JVM executes in a single native task context • MVM in the profile level • Foreground and Background state • Resource management and policy • User experience • Multitasking safety • MIDlets in MVM environment
  50. 50. 2006 JavaOneSM Conference | Session TS-3742 | 50 Agenda MVM overview MVM in the configuration level MVM in the profile level • The Foreground and Background state • Resource management • Multitasking safety MIDlets in MVM environment Q&A
  51. 51. 2006 JavaOneSM Conference | Session TS-3742 | 51 Q&A
  52. 52. 2006 JavaOneSM Conference | Session TS-3742 | Dancing While Gaming— Multitasking VMs (MVM) on Real Devices Jae Hyou Lee Yaniv Shani Samsung Electronics Sun Microsystems, Inc. www.samsung.com www.sun.com TS-3742

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