Ts 3742
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This document discusses multitasking virtual machines (MVM) on real devices. It describes a joint project between Samsung Electronics and Sun Microsystems to deploy MVM based on Sun's JWC1.1.3. The document outlines concepts like tasks and isolates in the configuration level, and foreground and background states and resource management in the profile level. It provides guidelines for developing MIDlets in an MVM environment and ensuring multitasking safety. The overall goal is to allow running multiple applications simultaneously on devices for a better user experience.
Ts 3742
- 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. 2006 JavaOneSM Conference | Session TS-3742 | 2 Goal Deeper understanding of Multitasking VM implementation on real devices
- 3. 2006 JavaOneSM Conference | Session TS-3742 | 3 Project Highlights A joint collaboration between Samsung Electronics and Sun Microsystems MVM deployment is based on Suns JWC1.1.3 Deploying most of the MSA JSRs Tested with hundreds of games and applications from leading content providers
- 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. 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. 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. 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. 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. 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. 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. 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. 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 Isnt Allowed
- 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. 2006 JavaOneSM Conference | Session TS-3742 | 14 Resource ManagementScheduling 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. 2006 JavaOneSM Conference | Session TS-3742 | 15 Resource ManagementMemory 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. 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. 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. 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. 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. 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. 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. 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. 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. 2006 JavaOneSM Conference | Session TS-3742 | 24 DEMO User Experience Demonstration
- 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. 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. 2006 JavaOneSM Conference | Session TS-3742 | 27 Managing Resources Mechanisms Reservation Quota Revocation Policies Fixed partition Open for competition Special cases
- 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. 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. 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 doesnt always have a dramatic effect on the MIDlets execution Revocation
- 31. 2006 JavaOneSM Conference | Session TS-3742 | 31 Resource Management Policies Initial amount of resources are reserved before MIDlet launch Resource availability validation during MIDlets startup Ensure consistent MIDlet behavior Fixed Partition
- 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. 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 arent honored when invoked from a Background MIDlet LCD Display
- 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. 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. 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. 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. 2006 JavaOneSM Conference | Session TS-3742 | 38 DEMO Resource Policy Demonstration
- 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. 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 Suns JWC software is multitasking safe
- 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 Isnt Allowed
- 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. 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. 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. doesnt offer APIs for MIDlet that doesnt use the Canvas class facilities MIDlet State Detection
- 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. 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 arent 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. 2006 JavaOneSM Conference | Session TS-3742 | 47 MIDlet Guidelines Return resources when you are done with them, dont 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. 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. 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. 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. 2006 JavaOneSM Conference | Session TS-3742 | 51 Q&A
- 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