ADR-0023 D9.7: IPCQ slot-memory latency model (TCM/SRAM/HBM)

Charge per-tier bandwidth + setup overhead at IPCQ slot WRITE
(receiver inbound DMA, in pe_dma._handle_ipcq_inbound) and slot
READ (recv consume, in pe_ipcq._handle_recv). Tier table
(common/ipcq_types.py):
  tcm  : 512 GB/s, 0 ns
  sram : 128 GB/s, 2 ns
  hbm  :  32 GB/s, 6 ns

Before this change, slot read/write was free regardless of
buffer_kind, making memory-tier choice invisible in simulated
latency. After the change, swapping buffer_kind in ccl.yaml
produces measurable per-tier separation in allreduce latency.

Tests:
  test_ipcq_buffer_kind_latency.py — three micro-tests asserting
    tcm < sram < hbm ordering, payload-scaling, and that
    buffer_kind sensitivity grows with payload (credit-only path
    stays fabric-bound).
  test_allreduce_buffer_kind_sweep.py — 12-config parametrized
    sweep emitting buffer_kind_sweep.png (3 lines, torus_2d).

conftest sessionfinish hook generalised to dispatch multiple
sweep aggregators (allreduce + buffer-kind).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -27,23 +27,27 @@ def pytest_sessionfinish(session, exitstatus):
     import sys
     from pathlib import Path
 
-    mod_path = Path(__file__).parent / "test_allreduce_multidevice.py"
-    if not mod_path.exists():
-        return
-    spec = importlib.util.spec_from_file_location(
-        "_test_allreduce_multidevice_for_aggregate", mod_path,
-    )
-    if spec is None or spec.loader is None:
-        return
-    mod = importlib.util.module_from_spec(spec)
-    sys.modules[spec.name] = mod
-    try:
-        spec.loader.exec_module(mod)
-        agg = getattr(mod, "_aggregate_sweep_plots", None)
-        if agg is not None:
-            agg()
-    except Exception as e:
-        print(f"[conftest] sweep aggregation failed: {e}")
+    def _exec(name: str, attr: str) -> None:
+        mod_path = Path(__file__).parent / name
+        if not mod_path.exists():
+            return
+        s = importlib.util.spec_from_file_location(
+            f"_{name.removesuffix('.py')}_for_aggregate", mod_path,
+        )
+        if s is None or s.loader is None:
+            return
+        mod = importlib.util.module_from_spec(s)
+        sys.modules[s.name] = mod
+        try:
+            s.loader.exec_module(mod)
+            fn = getattr(mod, attr, None)
+            if fn is not None:
+                fn()
+        except Exception as e:
+            print(f"[conftest] aggregator {attr}() in {name} failed: {e}")
+
+    _exec("test_allreduce_multidevice.py", "_aggregate_sweep_plots")
+    _exec("test_allreduce_buffer_kind_sweep.py", "aggregate_buffer_kind_plot")
 
 
 @pytest.fixture(scope="session")