PDC09 – Pre-conference – Windows 7 Bootcamp Part 2/6 – Core Kernel Changes

More Core Platform Support

• Supporting Mode than 64Lps
  • Introduction of the Processor Groups
    • Windows Server 2008 R2 introduces processor Groups
      • Each processor groups can contain up to 64 LPs
      • System support up to 4 groups in this release
      • Maintains compatibility with legacy systems
• Processes and Threads
  • Processes can  contain threads executing in multiple groups
  • Processes are assigned groups in round robin fashion
  • Threads are assigned to a group based on:
    • Inheritance from creating thread
    • Using new group affinity API
• Task Based Scheduling
  • Runtime support task based concurrency want to control when and where tasks execute
  • Why not use kernel threads to represent tasks
    • Context switches between threads involve the kernel scheduler
    • Runtime loses control when blocking event occurs
• UMS – User Mode Scheduling
  • Enables switching between threads in user mode
  • Returns control to the runtime when a thread blocks in the kernel
  • Architecture
    • Divides threads into a user and kernel portion
      • Together these comprise a UMS Worker Thread
    • Creates to views of what is being made
    • When a Worker thread enters the kernel
      • porting of the Scheduler thread enters wait state
      • Worker thread wakes and executes kernel service
        • Ensures correct kernel state for the Worker Thread
• The Dispatcher Lock
  • Dispatcher database lock originally protected the integrity of all scheduler related data structures
  • Over time additional locks introduced to reduce contention
    • Thread locks, timer table locks, PRCB locks
    • Still synchronizes
  • Replaced in Windows 7 by Coarse-Grained lock
    • Well defined locking hierarchy
    • Per-object locking used for object paths
    • Many Operations are lock-free
    • Uses transactional semantics for waits