docs(plugin-arch): 归档插件架构迁移评估 + plan 第11节整改计划

- docs/zh/架构迁移评估.md: C ABI→子进程+共享内存完整迁移论证(1621行)
- docs/zh/experiments/: 18项可复跑可行性实验(架构评估的所有数字来源)
- plan.md §11: 11.1~11.9 插件架构缺陷修复清单(唯一权威编号)
- main 保持干净,本批次为 update 特性分支的整改起点

docs/zh/experiments/plugin-arch/02-feasibility/exp4.go

@@ -0,0 +1,71 @@
+//go:build ignore
+package main
+
+import (
+	"fmt"
+	"os"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+type ring struct {
+	writeSeq atomic.Uint64
+	cap      uint64
+	slots    []uint64
+}
+
+func main() {
+	fmt.Println("=== 实验 4：事件环 post-and-forget vs 同步 Publish（慢消费者场景）===")
+	const tokens = 5000
+
+	// --- A. 现状：同步 Publish，消费者慢 ---
+	slowHandler := func() { time.Sleep(20 * time.Microsecond) }
+	t0 := time.Now()
+	for i := 0; i < tokens; i++ { slowHandler() }
+	syncDur := time.Since(t0)
+	fmt.Printf("A 同步 Publish (慢消费者 20µs): %d token 耗时 %v  → 均摊 %.1f µs/token\n",
+		tokens, syncDur, float64(syncDur.Microseconds())/tokens)
+
+	// --- B. 新方案：写环 + eventfd post，不等消费者 ---
+	r := &ring{cap: 1024, slots: make([]uint64, 1024)}
+	efd, _ := unix.Eventfd(0, unix.EFD_NONBLOCK)
+	f := os.NewFile(uintptr(efd), "e")
+
+	var dropped atomic.Uint64
+	// 慢消费者 goroutine
+	done := make(chan struct{})
+	go func() {
+		buf := make([]byte, 8)
+		var readSeq uint64
+		for {
+			if _, err := f.Read(buf); err != nil { return }
+			w := r.writeSeq.Load()
+			if w-readSeq > r.cap {
+				dropped.Add(w - readSeq - r.cap)
+				readSeq = w - r.cap
+			}
+			for readSeq < w { readSeq++ }
+			time.Sleep(20 * time.Microsecond) // 慢
+			select { case <-done: return; default: }
+		}
+	}()
+
+	t0 = time.Now()
+	one := []byte{1,0,0,0,0,0,0,0}
+	for i := 0; i < tokens; i++ {
+		s := r.writeSeq.Add(1)
+		r.slots[s%r.cap] = s      // 写数据
+		f.Write(one)              // post，不等
+	}
+	asyncDur := time.Since(t0)
+	close(done)
+	fmt.Printf("B 环+eventfd post:            %d token 耗时 %v  → 均摊 %.2f µs/token\n",
+		tokens, asyncDur, float64(asyncDur.Microseconds())/tokens)
+	fmt.Printf("\n加速比 %.1fx   丢弃事件 %d（消费者跟不上，已计数）\n",
+		float64(syncDur)/float64(asyncDur), dropped.Load())
+	if asyncDur < syncDur/5 {
+		fmt.Println("✅ post-and-forget 使流式发布与消费者速度解耦")
+	}
+}