Building ResourceAware Applications and Systems

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Building Resource-Aware Applications and Systems

• Michael B. Jones
• Microsoft Research

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Goal Coexisting Independent Real-Time
Applications

• Independently developed
• Predictable concurrent execution of
• real-time and non-real-time apps
• Meeting all apps timing needs
• Informing apps when not possible

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Overview

• Review
• Need for Resource Management
• Motivating Examples
• Resource Awareness
• New
• Systems support for resource-aware applications
  and systems
• Call to Action

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Case for Explicit Resource Allocation and
Accounting

• Time-sensitive applications need
• different resources
• at different rates
• in different amounts
• Even infinite resources insufficient if not given
  to apps in timely fashion

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Assumption Multiple Tasks

• Assumption
• Multiple concurrent tasks
• At least one time-sensitive
• Many such tasks to choose from
• Media input, output
• Speech, vision-based UIs
• Software modems, sound cards, ...
• Industrial device control
• etc.

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One Real-Time Task Enough

• Time-aware resource management needed even if
  just one real-time task
• Competing normal tasks can still cause real-time
  task to fail
• Round-robin with to large a period
• Fair share with too small a proportion

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Motivating Examples

• Speech, vision based intelligent UIs
• All the resources all the time
• Low-latency response required
• Reducing PC costs via soft migration
• Soft modems, soft ADSL, etc.
• Reliability
• Contain denial of service attacks
• Consumer real-time applications
• Coexist with independently developed real-time
  and non-real-time applications

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Resource Awareness

• Only apps know their timing requirements
• must have a vocabulary for expressing them
• Only system can enforce resource guarantees
• must do resource accounting
• to fulfill negotiated resource guarantees
• Both must be Resource Aware

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Building Resource-Aware Applications and Systems

• Resource management uses negotiation among three
  parties
• Applications
• Resource consumers
• Resource Planner
• Locus of policy decisions
• Acts on users behalf
• Resource Providers
• Scheduler, memory manager, net bandwidth, etc.

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Resource Management
Activity
Resource Planner
(ScsiDisk, 60) (CPU, 30) (ATM, 20) ...
(Activity, 30)
(Activity, 20)
(Activity, 60)
IResource
IResource
CPU
ATM Adapter
ICpu
IAtmCard
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Determining Application Resource Needs

• Adaptive approach
• 1. Observe own resource usage
• 2. Compute expected needs from past observations
• 3. Reserve appropriate resource amounts
• Resource self-aware applications key
• Only apps have knowledge to make appropriate
  resource tradeoffs
• Uncertainty in amounts inherent
• Caches, busses, CPU speeds, contention

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Using Resources
Activity
Resource Planner
Constraint-based Requests
Quality-of-service Streaming
IResource
IResource
CPU
ATM Adapter
ICpu
IAtmCard
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Resource Negotiation
Another Activity
Reserve!
Activity
Resource Planner
Negotiate
Persistent Overload!
IResource
IResource
CPU
ATM Adapter
ICpu
IAtmCard
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Tying It All Together

• OS Results
• Built, studied effective mechanisms for
  scheduling and resource management
• Separation of mechanism and policy
• Allows Resource Planner to manage resources on
  users behalf
• Decision Theory, User Modeling
• Provides effective means for planner to determine
  appropriate policies
• Goal maximizing value perceived by user
• User-aware UIs need these results!

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Missing Information Paths

• In current general-purpose systems
• Apps cant tell system
• when code needs to be executed
• amounts of resources they need
• System cant tell apps
• whether deadlines will be met
• amounts of resources available to them
• Both flying blind

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Call To Action

• Future systems must provide
• Explicit resource management interfaces
• Predictable low-latency scheduling
• Enabling technology for
• User interface advances
• Reduced cost computing
• More reliable computing
• Consumer real-time applications

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Building Resource-Aware Applications and Systems

• Discussion

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For More Information

• Contact me
• Mike Jones, mbj_at_microsoft.com
• Or see
• http//research.microsoft.com/mbj/

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Back Pocket Slides...
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Scheduling Research

• CPU scheduling built on Rialto OS
• Research version of MMOSA ITV OS
• Provides both
• Ongoing CPU Reservations
• Guarantee at least X time every Y time period
• Fine-grained Deadline Scheduling
• Do estimate work within time interval

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CPU Reservation

• Guaranteed execution rate and granularity for an
  activity
• X units of time out of every Y units, e.g.
• 800µs every 5ms
• 7.5ms every 33.3ms
• one second every minute
• Continuously guaranteed

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Time Constraint

• Deadline-based thread execution
• Guarantees execution within interval, or
• Proactively denies constraint request

schedulable BeginConstraint (time_interval,
estimate) if (schedulable) then Do normal work
under constraint else Transient overload -- shed
load if possible time_taken EndConstraint ()
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Adding Reservations to Existing Apps
CPU reservations improve performance

• 1 MPEG 5 AVI players, with reservations on
  Rialto