diff --git a/_prof.entry.ts b/_prof.entry.ts
new file mode 100644
index 0000000..8f0d1cb
--- /dev/null
+++ b/_prof.entry.ts
@@ -0,0 +1,8 @@
+import { readFileSync } from 'fs';
+import { fontSubset } from './backend/font_util/font.js';
+const buf = readFileSync('font/令东齐伋复刻体.ttf');
+const ab = buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
+const text = '天地玄黄宇宙洪荒日月盈昃辰宿列张寒来暑往秋收冬藏闰余成岁律吕调阳云腾致雨露结为霜金生丽水玉出昆冈剑号巨阙珠称夜光果珍李柰菜重芥姜海咸河淡鳞潜羽翔';
+fontSubset(ab, text, { sourceType: 'ttf', outType: 'ttf' });
+const N = 500;
+for (let i = 0; i < N; i++) fontSubset(ab, text, { sourceType: 'ttf', outType: 'ttf' });
diff --git a/_speed.entry.ts b/_speed.entry.ts
new file mode 100644
index 0000000..7f5d9df
--- /dev/null
+++ b/_speed.entry.ts
@@ -0,0 +1,16 @@
+import { performance } from 'perf_hooks';
+import { readFileSync } from 'fs';
+import { fontSubset } from './backend/font_util/font.js';
+const buf = readFileSync('font/令东齐伋复刻体.ttf');
+const ab = buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
+const cases: [string,string,any][] = [
+  ['千字文woff2','天地玄黄宇宙洪荒日月盈昃辰宿列张寒来暑往秋收冬藏闰余成岁律吕调阳云腾致雨露结为霜金生丽水玉出昆冈剑号巨阙珠称夜光果珍李柰菜重芥姜海咸河淡鳞潜羽翔',{sourceType:'ttf',outType:'woff2'}],
+  ['千字文ttf','天地玄黄宇宙洪荒日月盈昃辰宿列张寒来暑往秋收冬藏闰余成岁律吕调阳云腾致雨露结为霜金生丽水玉出昆冈剑号巨阙珠称夜光果珍李柰菜重芥姜海咸河淡鳞潜羽翔',{sourceType:'ttf',outType:'ttf'}],
+];
+for (const [label,text,opt] of cases) {
+  fontSubset(ab, text, opt);
+  const N = 300;
+  const t0 = performance.now();
+  for (let i=0;i<N;i++) fontSubset(ab, text, opt);
+  console.log(`${label.padEnd(14)} avg=${((performance.now()-t0)/N).toFixed(3)}ms`);
+}
diff --git a/vendor/fonteditor-core/lib/nodejs/buffer.js b/vendor/fonteditor-core/lib/nodejs/buffer.js
index 8b43c17..cdc2e57 100644
--- a/vendor/fonteditor-core/lib/nodejs/buffer.js
+++ b/vendor/fonteditor-core/lib/nodejs/buffer.js
@@ -30,16 +30,15 @@ var _default = exports.default = {
    * @param {ArrayBuffer} arrayBuffer 缓冲数组
    * @return {Buffer}
    */
+  /**
+   * 优化311: ArrayBuffer→Buffer 用 Buffer.from 共享底层内存（零拷贝），
+   * 替代逐字节 view.getUint8 循环（千字文 ttf 162KB 输出时为 toBuffer 9% 热点）。
+   * write 产出的 ArrayBuffer 后续不再修改，共享安全。
+   */
   toBuffer: function toBuffer(arrayBuffer) {
     if (Array.isArray(arrayBuffer)) {
       return Buffer.from(arrayBuffer);
     }
-    var length = arrayBuffer.byteLength;
-    var view = new DataView(arrayBuffer, 0, length);
-    var buffer = Buffer.alloc(length);
-    for (var i = 0, l = length; i < l; i++) {
-      buffer[i] = view.getUint8(i, false);
-    }
-    return buffer;
+    return Buffer.from(arrayBuffer);
   }
 };
\ No newline at end of file