From 6c70f6e7644d7d386a66c9dd4315e9c16678b42f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCrg=C3=BCn=20Day=C4=B1o=C4=9Flu?= <hey@gurgun.day>
Date: Sun, 6 Sep 2026 11:40:50 +0200
Subject: [PATCH] stream: amortize writable buffer compaction
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Signed-off-by: Gürgün Dayıoğlu <hey@gurgun.day>
Assisted-by: Codex
---
 benchmark/streams/writable-buffered-drain.js | 25 ++++++++++++++++++++
 lib/internal/streams/writable.js             |  2 +-
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 benchmark/streams/writable-buffered-drain.js

diff --git a/benchmark/streams/writable-buffered-drain.js b/benchmark/streams/writable-buffered-drain.js
new file mode 100644
index 000000000000..5ebed16624ea
--- /dev/null
+++ b/benchmark/streams/writable-buffered-drain.js
@@ -0,0 +1,25 @@
+'use strict';
+
+const common = require('../common');
+const { Writable } = require('stream');
+
+const bench = common.createBenchmark(main, {
+  count: [1024, 16384, 65536],
+  n: [100],
+});
+
+function main({ count, n }) {
+  const chunk = {};
+  let callback;
+  const stream = new Writable({
+    objectMode: true,
+    write(chunk, encoding, cb) { callback = cb; },
+  });
+
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    for (let j = 0; j < count; j++) stream.write(chunk);
+    for (let j = 0; j < count; j++) callback();
+  }
+  bench.end(n);
+}
diff --git a/lib/internal/streams/writable.js b/lib/internal/streams/writable.js
index 47e003ea3a8a..09d713f8a1fe 100644
--- a/lib/internal/streams/writable.js
+++ b/lib/internal/streams/writable.js
@@ -787,7 +787,7 @@ function clearBuffer(stream, state) {
 
     if (i === buffered.length) {
       resetBuffer(state);
-    } else if (i > 256) {
+    } else if (i > 256 && i * 2 >= buffered.length) {
       buffered.splice(0, i);
       state.bufferedIndex = 0;
     } else {