perf(ext/node): native vectored write for server streams (#19752)

```
# main
$ ./load_test 10 0.0.0.0 8080 0 0
Using message size of 20 bytes
Running benchmark now...
Msg/sec: 106182.250000
Msg/sec: 110279.750000
^C

# this PR
$ ./load_test 10 0.0.0.0 8080 0 0
Using message size of 20 bytes
Running benchmark now...
Msg/sec: 131632.250000
Msg/sec: 134754.250000
^C
```

ext/http/http_next.rs

@@ -32,6 +32,7 @@ use deno_core::ByteString;
 use deno_core::CancelFuture;
 use deno_core::CancelHandle;
 use deno_core::CancelTryFuture;
+use deno_core::JsBuffer;
 use deno_core::OpState;
 use deno_core::RcRef;
 use deno_core::Resource;
@@ -1034,6 +1035,34 @@ impl UpgradeStream {
     .try_or_cancel(cancel_handle)
     .await
   }
+
+  async fn write_vectored(
+    self: Rc<Self>,
+    buf1: &[u8],
+    buf2: &[u8],
+  ) -> Result<usize, AnyError> {
+    let mut wr = RcRef::map(self, |r| &r.write).borrow_mut().await;
+
+    let total = buf1.len() + buf2.len();
+    let mut bufs = [std::io::IoSlice::new(buf1), std::io::IoSlice::new(buf2)];
+    let mut nwritten = wr.write_vectored(&bufs).await?;
+    if nwritten == total {
+      return Ok(nwritten);
+    }
+
+    // Slightly more optimized than (unstable) write_all_vectored for 2 iovecs.
+    while nwritten <= buf1.len() {
+      bufs[0] = std::io::IoSlice::new(&buf1[nwritten..]);
+      nwritten += wr.write_vectored(&bufs).await?;
+    }
+
+    // First buffer out of the way.
+    if nwritten < total && nwritten > buf1.len() {
+      wr.write_all(&buf2[nwritten - buf1.len()..]).await?;
+    }
+
+    Ok(total)
+  }
 }
 
 impl Resource for UpgradeStream {
@@ -1048,3 +1077,16 @@ impl Resource for UpgradeStream {
     self.cancel_handle.cancel();
   }
 }
+
+#[op]
+pub async fn op_raw_write_vectored(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  buf1: JsBuffer,
+  buf2: JsBuffer,
+) -> Result<usize, AnyError> {
+  let resource: Rc<UpgradeStream> =
+    state.borrow().resource_table.get::<UpgradeStream>(rid)?;
+  let nwritten = resource.write_vectored(&buf1, &buf2).await?;
+  Ok(nwritten)
+}

ext/http/lib.rs

@@ -120,6 +120,7 @@ deno_core::extension!(
     http_next::op_http_track,
     http_next::op_http_upgrade_websocket_next,
     http_next::op_http_upgrade_raw,
+    http_next::op_raw_write_vectored,
     http_next::op_http_try_wait,
     http_next::op_http_wait,
   ],

ext/node/polyfills/internal/stream_base_commons.ts

@@ -253,7 +253,9 @@ export function onStreamRead(
       }
     } else {
       const offset = streamBaseState[kArrayBufferOffset];
-      const buf = Buffer.from(arrayBuffer, offset, nread);
+      // Performance note: Pass ArrayBuffer to Buffer#from to avoid
+      // copy.
+      const buf = Buffer.from(arrayBuffer.buffer, offset, nread);
       result = stream.push(buf);
     }
 

ext/node/polyfills/internal_binding/stream_wrap.ts

@@ -40,6 +40,9 @@ import {
 } from "ext:deno_node/internal_binding/async_wrap.ts";
 import { codeMap } from "ext:deno_node/internal_binding/uv.ts";
 
+const core = globalThis.Deno.core;
+const { ops } = core;
+
 interface Reader {
   read(p: Uint8Array): Promise<number | null>;
 }
@@ -54,7 +57,7 @@ export interface Closer {
 
 type Ref = { ref(): void; unref(): void };
 
-enum StreamBaseStateFields {
+const enum StreamBaseStateFields {
   kReadBytesOrError,
   kArrayBufferOffset,
   kBytesWritten,
@@ -195,6 +198,31 @@ export class LibuvStreamWrap extends HandleWrap {
     chunks: Buffer[] | (string | Buffer)[],
     allBuffers: boolean,
   ): number {
+    const supportsWritev = this.provider === providerType.TCPSERVERWRAP;
+    // Fast case optimization: two chunks, and all buffers.
+    if (chunks.length === 2 && allBuffers && supportsWritev) {
+      // String chunks.
+      if (typeof chunks[0] === "string") chunks[0] = Buffer.from(chunks[0]);
+      if (typeof chunks[1] === "string") chunks[1] = Buffer.from(chunks[1]);
+
+      ops.op_raw_write_vectored(
+        this[kStreamBaseField]!.rid,
+        chunks[0],
+        chunks[1],
+      ).then((nwritten) => {
+        try {
+          req.oncomplete(0);
+        } catch {
+          // swallow callback errors.
+        }
+
+        streamBaseState[kBytesWritten] = nwritten;
+        this.bytesWritten += nwritten;
+      });
+
+      return 0;
+    }
+
     const count = allBuffers ? chunks.length : chunks.length >> 1;
     const buffers: Buffer[] = new Array(count);