Workflow for 3.12 cycle

(Graphical version at the end)

Multi-core Python

A per-interpreter GIL

• Per-interpreter isolation for extension modules

• A CI check to prevent new globals in CPython code

  • Tooling to identify global variables in CPython code

• Interpreter isolation (_PyRuntimeState -> PyInterpreterState)

  • Consolidate global state to _PyRuntimeState

    • Tooling to identify global variables in CPython code (also above)

  • PEP 683 - immortal objects

  • mimalloc

• Restrictions on interpreter capability (e.g. no threading)

  • Per-interpreter config & func to specify restrictions

• PEP 684: A Per-interpreter GIL

Expose multiple interpreters to Python code

• Implement PEP 554

  • PEP 554 - Multiple Interpreters in the Stdlib

Reduced Reference Count Overhead

Reduced reference counting overhead

• Optimize flow of references in C, transferring ownership when needed

  • Identify flow of references in C

• Static reduction in refcount operations

  • Bytecode compiler enhancements Irit

  • Deferred reference counts

• Deferred reference counts (also above)

Compact Objects

Compact objects

• Merge managed dict and values pointer into one word

• One word GC header

  • Saturating refcounts

Specialization

Finish specialization

• Specialize SEND

  • Specialize FOR_ITER for generator

    • Specialize FOR_ITER for sequences Dennis

    • Shim frames on entry to PyEval_EvalDefault

      • Identify main sources of calls to PyEval_EvalFrame

  • Move PEP 380 logic into compiler Brandt

Trace optimized interpreter

Projected (short) trace opimized interpreter

TBD

graph LR

%% High level goals

    CompactObject[["Compact objects"]]
    
    ReducedRefcount[["Reduced reference counting overhead"]]
    
    SpecDone[["Finish specialization"]]
    
    Traces[["Projected (short) trace opimitized interpreter"]]

    InterpretersInPythonCode[["Expose multiple interpreters to Python code"]]

    PerInterpreterGIL[["A per-interpreter GIL"]]

%% Tasks

    Compiler("Bytecode compiler enhancements<br/><b>Irit</b>")
    
    StaticRefcntReduction("Use static analysis to reduce<br/>reference count operations")

    SpecSeq("Specialize FOR_ITER for sequences<br/><b>Dennis</b>")

    SpecGen("Specialize FOR_ITER for generator")
    
    SpecClass("Specialize CALL for Python classes")
    
    CtoPy("Identify main sources of<br/>calls to PyEval_EvalFrame")

    ShimFrame("Shim frames on entry<br/>to PyEval_EvalDefault")

    SpecSend("Specialize SEND")
    
    SatRefcnt("Saturating refcounts")

    380("Move PEP 380 logic into compiler<br/><b>Brandt</b> ")

    EncapsulateGIL("Encapasulate GIL code and<br/>move it out of ceval.c #93177")

    OpcodesOwnFile("Move opcode definitions to their own file<br/>and generate PyEval_EvalDefault")

    CycleGC("Improve cycle GC<br/>(Task needs breaking up)")

    MiniOps("Breakup instruction definitions into 'mini-ops'")
    
    SmallGCHead("One word GC header")
    
    MergeDictValuePointers("Merge managed dict and values<br/>pointer into one word")
 
    TrackRefsInC("Identify flow of references in C")
    
    OptRefsInC("Optimize flow of references in C,<br/>transferring ownership when needed")
    
    GuardOpt("Optimize traces:<br/>Guard stengthening and elimination")
    
    AllocSinking("Optimize traces:<br/>Allocation elimination")
    
    AllBranchesForward("Only unconditional jumps should go backwards")
    
    HotSpotDetection("Detect hotspots in code")
    
    TraceProjection("Trace projection:<br/>Create traces from hotspots")
    
    TraceEval("Trace interpreter")
    
    OptAPI("Implement optimizer API")
    
    Deferred("Deferred reference counts")
    
    StaticRefcntReduction("Static reduction in refcount operations")
    
    WebAssemblyFriendlyInterpreter("Generate version of the interpreter better<br/>suited to emscripten and web assembly")

    PEP554("PEP 554 - Multiple Interpreters in the Stdlib")

    PEP554Impl("Implement PEP 554")

    ExtensionIsolation("Per-interpreter isolation for extension modules")

    CAnalyzer("Tooling to identify global variables in CPython code")

    GlobalsCICheck("A CI check to prevent new globals in CPython code")

    ConsolidateGlobals("Consolidate global state to _PyRuntimeState")

    ImmortalObjects("PEP 683 - immortal objects")

    Mimalloc("mimalloc")

    InterpreterIsolation("Interpreter isolation (_PyRuntimeState -> PyInterpreterState)")

    InterpretersAPI("Per-interpreter config & func to specify restrictions")

    InterpreterRestrictions("Restrictions on interpreter capability (e.g. no threading)")

    PEP684("PEP 684 - A Per-Interpreter GIL")

%% Dependencies

    380 --> OpcodesOwnFile
    380 --> SpecSend

    subgraph Trace optimized interpreter
    AllBranchesForward --> HotSpotDetection
    HotSpotDetection --> TraceProjection
    OpcodesOwnFile --> MiniOps
    EncapsulateGIL --> OpcodesOwnFile
    OpcodesOwnFile --> WebAssemblyFriendlyInterpreter
    OptAPI --> TraceProjection
    MiniOps --> TraceProjection
    TraceProjection --> TraceEval
    MiniOps --> TraceEval
    TraceEval --> GuardOpt
    TraceEval --> AllocSinking
    GuardOpt --> Traces
    AllocSinking --> Traces
    end

    subgraph Specialization
    CtoPy --> ShimFrame
    SpecSeq --> SpecGen
    ShimFrame --> SpecGen
    SpecGen --> SpecSend
    SpecSend --> SpecDone
    SpecClass --> SpecDone
    end

    subgraph Compact Objects
    SatRefcnt --> SmallGCHead
    MergeDictValuePointers --> CompactObject
    SmallGCHead --> CompactObject
    end

    subgraph Reduced Reference Count Overhead
    TrackRefsInC --> OptRefsInC
    OptRefsInC --> ReducedRefcount
    Compiler --> StaticRefcntReduction
    Deferred --> StaticRefcntReduction
    Deferred --> ReducedRefcount
    StaticRefcntReduction --> ReducedRefcount
    end

    subgraph Multi-core Python
    ExtensionIsolation --> PerInterpreterGIL
    CAnalyzer --> ConsolidateGlobals
    CAnalyzer --> GlobalsCICheck
    GlobalsCICheck --> PerInterpreterGIL
    ConsolidateGlobals --> InterpreterIsolation
    ImmortalObjects --> InterpreterIsolation
    Mimalloc --> InterpreterIsolation
    InterpreterIsolation --> PerInterpreterGIL
    InterpretersAPI --> InterpreterRestrictions
    InterpreterRestrictions --> PerInterpreterGIL
    PEP684 --> PerInterpreterGIL

    PEP554 --> PEP554Impl
    PEP554Impl --> InterpretersInPythonCode
    end

%% Links and colors
    click TrackRefsInC "https://github.com/faster-cpython/ideas/issues/441"
    click OptRefsInC "https://github.com/faster-cpython/ideas/issues/442"
    click Deferred "https://github.com/faster-cpython/ideas/issues/443"
    click StaticRefcntReduction "https://github.com/faster-cpython/ideas/issues/444"

    click ShimFrame "https://github.com/faster-cpython/ideas/issues/436"
    click SpecSeq "https://github.com/faster-cpython/ideas/issues/67"
    click SpecClass "https://github.com/python/cpython/pull/31707"

    click 380 "https://github.com/python/cpython/pull/31968"

    click MergeDictValuePointers "https://github.com/python/cpython/pull/95278"
    style MergeDictValuePointers fill:#88f

    click PEP554 "https://peps.python.org/pep-0554/"
    click ImmortalObjects "https://peps.python.org/pep-0683/"
    click PEP684 "https://peps.python.org/pep-0684/"

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