Towards Resource Aware Applications and Systems Michael B. Jones Microsoft Research

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

Overview  Need for Resource Management  Motivating Examples  Resource Awareness  Call to Action

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

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.

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

Motivation: User Interfaces  User interfaces can use all the resources, all the time!  Speech, vision understanding, implicit queries, etc. can use as much as they get  Must manage background activities’ resource usage so real work gets done  Low-latency responses required  Camera-based head motion parallax driving 3D virtual environment needs < 200ms response — ms ideal  Simple timesharing, priority schemes won’t get the right tasks done at the right times

Motivation: Reducing Costs  PC industry wants lower prices points  Buying choice different below ~$400  “Soft Migration” one means  Remove “extra” CPUs, such as modem DSP  $15 parts cost => ~$45 retail cost  Soft modems work well on 200MHz MMX  Sample processing rates  ~12ms in normal operation  ~1.5ms during training  Infeasible without appropriate scheduling

Motivation: Reliability  Denial of Service attacks steal resources  Resource management can guarantee resources to “good” clients  Example: Resource Container results protecting web servers from SIN attacks (Banga, Druschel, & Mogul: OSDI ’99)

Motivation: Consumer Real- Time Applications  Enable consumers to purchase or download applications  some of which have real-time needs  just like current shrink-wrapped & Internet applications today  with expectation independently developed apps will successfully coexist.

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

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

Missing Information Paths In current general-purpose systems:  Apps can’t tell system:  when code needs to be executed  amounts of resources they need  System can’t tell apps:  whether deadlines will be met  amounts of resources available to them  Both flying blind

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

Towards Resource Aware Applications and Systems Discussion