Unified-routing A+B ablation: decode-aware LMetric + v3 anti-hotspot

cache_aware_proxy: add lmetric_decode_weight (decode-load penalty in the
LMetric fallback score) and a v3 anti-hotspot recent-migration penalty
(effective_load = num_req + recent-migration count over a sliding window),
preventing back-to-back migration clustering. UNIFIED_ABLATION.md documents
the A (overload_factor=1.3) + B' (decode-weight, max(num_req,1)) + RaceFix
sweep: A+B'+RaceFix reaches TTFT p90 7770ms, beating v3 PD-sep migration by
~20%. Runners/analyzer for the b3 trace replay included.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

microbench/connector_tax/cache_sweep/run_b3_replay.sh

@@ -0,0 +1,94 @@
+#!/usr/bin/env bash
+# B3 routing-policy reproducibility re-test.
+#
+# Re-runs the 5 routing policies from fig_b3_latency_bars.png on the same
+# trace, in a single same-day session, to check whether the ordering
+# (unified < load_only < sticky etc.) still holds today.
+#
+# Policies (in run order):
+#   lmetric        plain — cache-aware P_tokens × BS
+#   load_only      plain — pure min-num_requests
+#   sticky         plain — hard session affinity
+#   unified        plain — hybrid affinity + LMetric fallback
+#   unified_v2     Mooncake kv_both + selective PD-sep (with DR-fix applied)
+#
+# unified_v2 is run with VLLM_MOONCAKE_DISABLE_DIRECT_READ_SYNC=1 so we
+# get the "best Mooncake state" we have today (DR-fix on top of the
+# already-fixed mainline after e3a1d70 etc.). The other 4 policies don't
+# load any connector so the patch is irrelevant.
+
+set -uo pipefail
+
+PROJ_DIR="${PROJ_DIR:-/home/admin/cpfs/wjh/agentic-kv}"
+TRACE="${TRACE:-$PROJ_DIR/traces/w600_r0.0015_st30.jsonl}"
+DATE="$(date +%Y%m%d_%H%M)"
+OUTROOT="${OUTROOT:-$PROJ_DIR/outputs/b3_replay_${DATE}}"
+PYTHON="$PROJ_DIR/.venv/bin/python"
+DR_FIX_SCRIPT="$PROJ_DIR/microbench/connector_tax/cache_sweep/apply_direct_read_fix.py"
+VLLM_ROOT="${VLLM_ROOT:-$PROJ_DIR/.venv/lib/python3.12/site-packages/vllm}"
+
+mkdir -p "$OUTROOT"
+echo "=== B3 5-policy re-test ==="
+echo "Trace : $TRACE"
+echo "Out   : $OUTROOT"
+echo "Order : lmetric → load_only → sticky → unified → unified_v2 (DR-fix on)"
+echo ""
+
+cleanup_all() {
+    pkill -9 -f cache_aware_proxy 2>/dev/null || true
+    pkill -9 -f "vllm serve" 2>/dev/null || true
+    pkill -9 -f "EngineCore" 2>/dev/null || true
+    sleep 5
+    "$PYTHON" "$DR_FIX_SCRIPT" --revert --vllm-root "$VLLM_ROOT" 2>/dev/null || true
+}
+trap cleanup_all EXIT
+cleanup_all
+
+# Apply DR-fix once — it's env-gated so only unified_v2 (with env=1) sees it
+echo "[stage 0] applying CT_DR_FIX (env-gated, only activates when VLLM_MOONCAKE_DISABLE_DIRECT_READ_SYNC=1)"
+"$PYTHON" "$DR_FIX_SCRIPT" --apply --vllm-root "$VLLM_ROOT"
+
+run_policy() {
+    local policy="$1"
+    local skip_dr="$2"
+    local rundir="$OUTROOT/$policy"
+    mkdir -p "$rundir"
+
+    echo ""
+    echo "====== $policy ; DR_SYNC_DISABLED=$skip_dr ======"
+
+    if [ "$skip_dr" = "1" ]; then
+        export VLLM_MOONCAKE_DISABLE_DIRECT_READ_SYNC=1
+    else
+        unset VLLM_MOONCAKE_DISABLE_DIRECT_READ_SYNC
+    fi
+
+    bash "$PROJ_DIR/scripts/b3_isolated_policy.sh" "$policy" "$TRACE" "$rundir" \
+        2>&1 | tee "$rundir/orchestrator.log" | tail -30
+    rc="${PIPESTATUS[0]}"
+    if [ "$rc" != "0" ]; then
+        echo "[FAIL] policy $policy rc=$rc"
+    fi
+    # Belt-and-braces cleanup between policies
+    pkill -9 -f cache_aware_proxy 2>/dev/null || true
+    pkill -9 -f "vllm serve" 2>/dev/null || true
+    pkill -9 -f "EngineCore" 2>/dev/null || true
+    sleep 10
+    return 0
+}
+
+run_policy "lmetric"    "0"
+run_policy "load_only"  "0"
+run_policy "sticky"     "0"
+run_policy "unified"    "0"
+run_policy "unified_v2" "1"  # uses Mooncake kv_both; activate DR-fix
+
+echo ""
+echo "[stage Z] reverting CT_DR_FIX"
+"$PYTHON" "$DR_FIX_SCRIPT" --revert --vllm-root "$VLLM_ROOT"
+
+echo ""
+echo "Done. Artifacts: $OUTROOT"
+for p in lmetric load_only sticky unified unified_v2; do
+    echo "  $p: $OUTROOT/$p/metrics.jsonl"
+done