Changes between Version 85 and Version 86 of LightweightConcurrency


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Timestamp:
May 22, 2012 10:07:46 PM (2 years ago)
Author:
kc
Comment:

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  • LightweightConcurrency

    v85 v86  
    3636But, why would we be interested in modifying GHC's concurrency environment? There are several good reasons to believe that a particular concurrent programming model, or a scheduling policy would not suit every application. With the emergence of many-core processors, we see NUMA effects becoming more prominent, and applications might benefit from NUMA aware scheduling and load balancing policies. Moreover, an application might have a better knowledge of the scheduling requirements -- a thread involved in user-interaction is expected to be given more priority over threads performing background processing. We might want to experiment with various work-stealing or work-sharing policies. More ambitiously, we might choose to build X10 style async-finish or Cilk style spawn-sync task parallel abstractions. Ideally, we would like allow the programmer to write an application that can  seamlessly combine all of these different programming abstractions, with pluggable scheduling and load balancing policies. 
    3737 
    38 While we want to provide flexibility to the Haskell programmer, this should not come at a cost of added complexity and decreased performance. This idea reflects in the synchronization abstractions exposed to the programmer - [#PTM Primitive Transactional Memory(PTM)]), and our decision to keep certain pieces of the concurrency puzzle in the RTS ([#SafeForeignFunctionInterface Safe FFI],[#Black-holeHandling Blackholes]). One would think lifting parts of the runtime system to Haskell, and retaining other parts in C, would complicate the interactions between the concurrency primitives and schedulers. We abstract the scheduler interface using PTM monads, which simplifies the interactions. The figure below captures the key design principles of the proposed system. 
     38While we want to provide flexibility to the Haskell programmer, this should not come at a cost of added complexity and decreased performance. This idea reflects in the synchronization abstractions exposed to the programmer - [#PTM Primitive Transactional Memory(PTM)]), and our decision to keep certain pieces of the concurrency puzzle in the RTS ([#SafeForeignCalls Safe Foreign Calls],[#Black-holeHandling Blackholes]). One would think lifting parts of the runtime system to Haskell, and retaining other parts in C, would complicate the interactions between the concurrency primitives and schedulers. We abstract the scheduler interface using PTM monads, which simplifies the interactions. The figure below captures the key design principles of the proposed system. 
    3939 
    4040[[Image(GHC_LWC_Key.jpg, 100%)]]