Add semaphore registry and admission gate REPLACE for adaptive concurrency (#1391)#1391
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Add semaphore registry and admission gate REPLACE for adaptive concurrency (#1391)#1391justinvjoseph wants to merge 3 commits into
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…earch#1389) Summary: Add `ResizableSemaphore` — an asyncio-compatible semaphore whose max permit count can be adjusted at runtime. This is the foundational primitive for dynamic concurrency control in SPDL pipelines. Key features: - `resize(new_max)` adjusts permits at runtime; resize-up wakes blocked waiters immediately, resize-down drains gracefully (no preemption) - `acquire()`/`release()` semantics match `asyncio.Semaphore` - `max_value` and `active` properties for observability - Thread-safe within asyncio's single-threaded model - Comprehensive error handling for invalid values This is Diff 1 of a 5-diff series implementing a unified adaptive scheduler for SPDL pipelines (T262755626). Differential Revision: D99920401
…ops (facebookresearch#1390) Summary: Introduces an opt-in priority scheduler that replaces the ThreadPoolExecutor's FIFO dispatch with a PriorityQueue. Deeper pipeline stages (closer to sink) are dispatched first, reducing pipeline bubble time and WIP. Key changes: - New `_scheduler.py` with `AdaptiveScheduler` class - `_PipeArgs` gains `nice` and `_depth` fields for priority control - `convert_to_async()` routes through scheduler when provided - `_build_node()` registers stages and intercepts sync ops - `build_pipeline()` gains `use_scheduler=True` flag - `PipelineBuilder.pipe()` gains `nice` parameter When `use_scheduler=False` (default), behavior is identical to today. Differential Revision: D99935461
…rency (facebookresearch#1391) Summary: This is Diff 3a in the T262755626 stack. Adds the foundation for runtime concurrency adjustment in SPDL pipelines: 1. `_PipelineImpl._semaphore_registry: dict[str, ResizableSemaphore]` — sibling registry keyed on the qualified stage name. Populated at pipeline build time when a stage opts in. NO modification to `StageInfo` (preserves frozen=True / hashability for third-party code). 2. `_PipelineImpl._dynamic_concurrency: dict[str, int]` — current value per stage; updated by future `Pipeline.resize_concurrency()` calls. 3. `_PipelineImpl._stage_info_by_name: dict[str, StageInfo]` — for error messages and future Track B logging hooks. 4. `_pipe()` admission gate REPLACE (V5.6): when a `ResizableSemaphore` is registered for a stage, `await semaphore.acquire()` becomes the admission gate, REPLACING the static `len(tasks) >= concurrency` check. When no semaphore is registered (the default), behaviour is unchanged — ZERO per-task overhead added to the existing fast path. The branch is taken ONCE outside the hot loop (dispatching to `_pipe_with_semaphore`). 5. `build_pipeline(_install_semaphores_for_test: bool = False)` test-only knob: when True, every Pipe stage is built with a `ResizableSemaphore` and registered. Production code MUST NOT pass this — it bypasses the selective opt-in semantics of `Pipeline.resize_concurrency` (Diff 3b). 6. V5.5 throughput regression test (`admission_gate_perf_test.py`): 4-stage sync pipeline, N=10000 items, 5 trials. Regression > 2% on either p50 or p99 fails the diff. Includes registry wiring smoke tests and an in-flight-cap assertion. Note (perf-reviewer WARN-1): the V5.5 perf test covers sync stages only — extending to async/sync_iter handlers is a follow-up after Diff 3a lands. Note (perf-reviewer WARN-2): qualified stage names == `info.stage_name` for non-MultiPipe stages. LCA's MultiPipe is a single SPDL Pipe with internal dispatcher; the `_qualified_name(branch_label=...)` scheme is forward-compatible for true SPDL fan-out. The user-facing API (`Pipeline.resize_concurrency`) lands in Diff 3b. Differential Revision: D102929216
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Summary:
This is Diff 3a in the T262755626 stack. Adds the foundation for runtime concurrency adjustment in SPDL pipelines:
_PipelineImpl._semaphore_registry: dict[str, ResizableSemaphore]— sibling registry keyed on the qualified stage name. Populated at pipeline build time when a stage opts in. NO modification toStageInfo(preserves frozen=True / hashability for third-party code)._PipelineImpl._dynamic_concurrency: dict[str, int]— current value per stage; updated by futurePipeline.resize_concurrency()calls._PipelineImpl._stage_info_by_name: dict[str, StageInfo]— for error messages and future Track B logging hooks._pipe()admission gate REPLACE (V5.6): when aResizableSemaphoreis registered for a stage,await semaphore.acquire()becomes the admission gate, REPLACING the staticlen(tasks) >= concurrencycheck. When no semaphore is registered (the default), behaviour is unchanged — ZERO per-task overhead added to the existing fast path. The branch is taken ONCE outside the hot loop (dispatching to_pipe_with_semaphore).build_pipeline(_install_semaphores_for_test: bool = False)test-only knob: when True, every Pipe stage is built with aResizableSemaphoreand registered. Production code MUST NOT pass this — it bypasses the selective opt-in semantics ofPipeline.resize_concurrency(Diff 3b).admission_gate_perf_test.py): 4-stage sync pipeline, N=10000 items, 5 trials. Regression > 2% on either p50 or p99 fails the diff. Includes registry wiring smoke tests and an in-flight-cap assertion.Note (perf-reviewer WARN-1): the V5.5 perf test covers sync stages only — extending to async/sync_iter handlers is a follow-up after Diff 3a lands.
Note (perf-reviewer WARN-2): qualified stage names ==
info.stage_namefor non-MultiPipe stages. LCA's MultiPipe is a single SPDL Pipe with internal dispatcher; the_qualified_name(branch_label=...)scheme is forward-compatible for true SPDL fan-out.The user-facing API (
Pipeline.resize_concurrency) lands in Diff 3b.Differential Revision: D102929216