From 0e36c43c64d2089e3af50d78b37e0ff12f083caa Mon Sep 17 00:00:00 2001
From: Devyn Cairns <devyn.cairns@gmail.com>
Date: Fri, 5 Apr 2024 20:52:27 -0700
Subject: [PATCH] Add BufWriter to ChildStdin on the plugin interface (#12419)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

# Description
This speeds up writing messages to the plugin, because otherwise every
individual piece of the messages (not even the entire message) is
written with one syscall, leading to a lot of back and forth with the
kernel.

I learned this by running `strace` to debug something and saw a ton of
`write()` calls.

```nushell
# Before
1..10 | each { timeit { example seq 1 10000 | example sum } } | math avg
269ms 779µs 149ns
# After
> 1..10 | each { timeit { example seq 1 10000 | example sum } } | math avg
39ms 636µs 643ns
```

# User-Facing Changes
- Performance improvement

# Tests + Formatting
- :green_circle: `toolkit fmt`
- :green_circle: `toolkit clippy`
- :green_circle: `toolkit test`
- :green_circle: `toolkit test stdlib`
---
 crates/nu-plugin/src/plugin/mod.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/crates/nu-plugin/src/plugin/mod.rs b/crates/nu-plugin/src/plugin/mod.rs
index 90253ab7a3..d314f3c54a 100644
--- a/crates/nu-plugin/src/plugin/mod.rs
+++ b/crates/nu-plugin/src/plugin/mod.rs
@@ -10,7 +10,7 @@ use std::{
     env,
     ffi::OsStr,
     fmt::Write,
-    io::{BufReader, Read, Write as WriteTrait},
+    io::{BufReader, BufWriter, Read, Write as WriteTrait},
     ops::Deref,
     path::Path,
     process::{Child, ChildStdout, Command as CommandSys, Stdio},
@@ -178,8 +178,9 @@ fn make_plugin_interface(
     let encoder = get_plugin_encoding(&mut stdout)?;
 
     let reader = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, stdout);
+    let writer = BufWriter::with_capacity(OUTPUT_BUFFER_SIZE, stdin);
 
-    let mut manager = PluginInterfaceManager::new(source.clone(), (Mutex::new(stdin), encoder));
+    let mut manager = PluginInterfaceManager::new(source.clone(), (Mutex::new(writer), encoder));
     manager.set_garbage_collector(gc);
 
     let interface = manager.get_interface();