From 367f46d7931db1871c7eb5f6bece64c1f2467b18 Mon Sep 17 00:00:00 2001
From: Steve Klabnik <steve@steveklabnik.com>
Date: Wed, 30 Sep 2015 13:35:33 -0400
Subject: [PATCH] Make note of performance implications of Read

Fixes #28073
---
 src/libstd/io/mod.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 54869807cac..a76755dadd3 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -370,6 +370,13 @@ fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize>
 /// throughout `std::io` take and provide types which implement the `Read`
 /// trait.
 ///
+/// Please note that each call to `read` may involve a system call, and
+/// therefore, using something that implements [`BufRead`][bufread], such as
+/// [`BufReader`][bufreader], will be more efficient.
+///
+/// [bufread]: trait.BufRead.html
+/// [bufreader]: struct.BufReader.html
+///
 /// # Examples
 ///
 /// [`File`][file]s implement `Read`: