MB5 PD ablation v2 tooling: conc completion-panel plot + gpu_monitor dep

- plot_pd_crossover.py fig_conc: lead with request-completion % (the honest
  collapse signal; latency percentiles count successes only), then mean-E2E /
  TPS; note PD-capped/colo-uncapped in the title.
- add microbench/fresh_setup/gpu_monitor.sh (referenced by the committed
  mb5_run_gpu.sh:73 for per-GPU util collection).

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

microbench/fresh_setup/gpu_monitor.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# Sample GPU utilization every 5s, output CSV
+# Usage: bash gpu_monitor.sh <output_file> [interval_s]
+#   Runs until killed (Ctrl+C or kill)
+
+OUT="${1:-/tmp/gpu_util.csv}"
+INTERVAL="${2:-5}"
+
+echo "timestamp,gpu,util_pct,mem_used_mb,mem_total_mb,power_w" > "$OUT"
+
+while true; do
+    TS=$(date +%s.%N)
+    nvidia-smi --query-gpu=index,utilization.gpu,memory.used,memory.total,power.draw \
+        --format=csv,noheader,nounits 2>/dev/null | while IFS=', ' read -r idx util mem_used mem_total power; do
+        echo "$TS,$idx,$util,$mem_used,$mem_total,$power"
+    done >> "$OUT"
+    sleep "$INTERVAL"
+done

microbench/fresh_setup/plot_pd_crossover.py

@@ -154,28 +154,33 @@ def fig_conc():
     g = by_axis(load("fig3_conc32k.json"),
                 lambda n: (int(m.group(1)) if (m := re.search(r"_N(\d+)_", n)) else None))
     xs = sorted(g)
-    fig, axes = plt.subplots(1, 3, figsize=(15, 4.2))
-    ax1, ax2, ax3 = axes
+    fig, (ax1, ax2, ax3) = plt.subplots(1, 3, figsize=(15, 4.2))
+
+    # (a) request completion % — the headline (latency percentiles count successes
+    # only, so they understate PD; completion is the honest collapse signal).
     for arm in ["colo", *PD_ARMS]:
-        ax1.plot(xs, series(g, xs, arm, "e2e_mean"), **STYLE[arm])
-    ax1.axhline(10.0, color="red", ls=":", lw=1, label="SLO (mean E2E 10s)")
-    ax1.set_yscale("log"); ax1.set_xticks(xs); ax1.set_xticklabels(xs, fontsize=7)
-    ax1.set_xlabel("concurrent sessions N"); ax1.set_ylabel("E2E latency mean (s, log)")
-    ax1.set_title("(a) mean-E2E vs concurrency"); ax1.legend(fontsize=8); ax1.grid(alpha=.3, which="both")
+        comp = [(g[x][arm]["n"] / g[x][arm]["req"] * 100) if arm in g[x] else None for x in xs]
+        ax1.plot(xs, comp, **STYLE[arm])
+    ax1.axhline(100, color="grey", ls=":", lw=1)
+    ax1.set_xticks(xs); ax1.set_xticklabels(xs, fontsize=7)
+    ax1.set_xlabel("concurrent sessions N"); ax1.set_ylabel("request completion (%)")
+    ax1.set_title("(a) completion: colo 100%, PD collapses"); ax1.legend(fontsize=8); ax1.grid(alpha=.3)
 
     for arm in ["colo", *PD_ARMS]:
-        ax2.plot(xs, series(g, xs, arm, "tps"), **STYLE[arm])
-    ax2.set_xticks(xs); ax2.set_xticklabels(xs, fontsize=7)
-    ax2.set_xlabel("concurrent sessions N"); ax2.set_ylabel("throughput (tok/s)")
-    ax2.set_title("(b) TPS: colo scales, PD plateaus/drops"); ax2.legend(fontsize=8); ax2.grid(alpha=.3)
+        ax2.plot(xs, series(g, xs, arm, "e2e_mean"), **STYLE[arm])
+    ax2.axhline(10.0, color="red", ls=":", lw=1, label="SLO 10s")
+    ax2.set_yscale("log"); ax2.set_xticks(xs); ax2.set_xticklabels(xs, fontsize=7)
+    ax2.set_xlabel("concurrent sessions N"); ax2.set_ylabel("E2E latency mean (s, log)")
+    ax2.set_title("(b) mean-E2E (successes only)"); ax2.legend(fontsize=8); ax2.grid(alpha=.3, which="both")
 
     for arm in ["colo", *PD_ARMS]:
-        ax3.plot(xs, [v * 100 if v is not None else None for v in series(g, xs, arm, "apc")], **STYLE[arm])
+        ax3.plot(xs, series(g, xs, arm, "tps"), **STYLE[arm])
     ax3.set_xticks(xs); ax3.set_xticklabels(xs, fontsize=7)
-    ax3.set_xlabel("concurrent sessions N"); ax3.set_ylabel("producer prefix-cache hit-rate (%)")
-    ax3.set_title("(c) APC vs concurrency"); ax3.legend(fontsize=8); ax3.grid(alpha=.3)
-    fig.suptitle("Fig 3 — Concurrency axis (in32768/out128, reuse~0.984): sweep N by 8 to the 10s-SLO ceiling",
-                 fontsize=11, y=1.02)
+    ax3.set_xlabel("concurrent sessions N"); ax3.set_ylabel("throughput (tok/s)")
+    ax3.set_title("(c) TPS"); ax3.legend(fontsize=8); ax3.grid(alpha=.3)
+    fig.suptitle("Fig 3 — Concurrency axis (in32768/out128, reuse~0.984, PD capped 600s / colo uncapped): "
+                 "colo degrades gracefully (100% completion), PD collapses earlier as N rises",
+                 fontsize=10, y=1.02)
     fig.tight_layout(); p = OUT / "fig3_concurrency_axis.png"; fig.savefig(p, dpi=130, bbox_inches="tight")
     print("wrote", p)