perf: use sendto syscalls (#19414)

This switches syscall used in HTTP and WS server from "writev"
to "sendto".

"DENO_USE_WRITEV=1" can be used to enable using "writev" syscall.
Doing this for easier testing of various setups.

Cargo.lock

@@ -1412,6 +1412,7 @@ dependencies = [
  "fastwebsockets",
  "http",
  "hyper 0.14.26",
+ "once_cell",
  "serde",
  "tokio",
  "tokio-rustls",

ext/http/http_next.rs

@@ -73,13 +73,13 @@ type Request = hyper1::Request<Incoming>;
 type Response = hyper1::Response<ResponseBytes>;
 
 static USE_WRITEV: Lazy<bool> = Lazy::new(|| {
-  let disable_writev = std::env::var("DENO_HYPER_USE_WRITEV").ok();
+  let enable = std::env::var("DENO_USE_WRITEV").ok();
 
-  if let Some(val) = disable_writev {
-    return val != "0";
+  if let Some(val) = enable {
+    return !val.is_empty();
   }
 
-  true
+  false
 });
 
 /// All HTTP/2 connections start with this byte string.

ext/websocket/Cargo.toml

@@ -21,6 +21,7 @@ deno_tls.workspace = true
 fastwebsockets = { workspace = true, features = ["upgrade"] }
 http.workspace = true
 hyper = { workspace = true, features = ["backports"] }
+once_cell.workspace = true
 serde.workspace = true
 tokio.workspace = true
 tokio-rustls.workspace = true

ext/websocket/lib.rs

@@ -27,6 +27,7 @@ use http::Method;
 use http::Request;
 use http::Uri;
 use hyper::Body;
+use once_cell::sync::Lazy;
 use serde::Serialize;
 use std::borrow::Cow;
 use std::cell::Cell;
@@ -50,9 +51,18 @@ use fastwebsockets::Frame;
 use fastwebsockets::OpCode;
 use fastwebsockets::Role;
 use fastwebsockets::WebSocket;
-
 mod stream;
 
+static USE_WRITEV: Lazy<bool> = Lazy::new(|| {
+  let enable = std::env::var("DENO_USE_WRITEV").ok();
+
+  if let Some(val) = enable {
+    return !val.is_empty();
+  }
+
+  false
+});
+
 #[derive(Clone)]
 pub struct WsRootStoreProvider(Option<Arc<dyn RootCertStoreProvider>>);
 
@@ -360,7 +370,7 @@ pub fn ws_create_server_stream(
     ),
     Role::Server,
   );
-  ws.set_writev(true);
+  ws.set_writev(*USE_WRITEV);
   ws.set_auto_close(true);
   ws.set_auto_pong(true);