December 2013
Intermediate to advanced
496 pages
8h 57m
Chinese
Content preview from LINUX系統程式設計 第二版
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第四章
進階檔案 I/O
第 2 章，我們看過了 Linux 的基本 I/O 系統呼叫。這些呼叫不僅是檔案 I/O 的基礎，也
是 Linux 上所有通訊的基礎。第 3 章，我們看過了基本 I/O 系統呼叫之上常常需要用到
「用戶空間緩衝機制」（user-space buffering），而且我們還研究了一個用戶空間緩衝方
案，也就是 C 語言的標準 I/O 程式庫。本章，我們將探討 Linux 所提供之較進階的 I/O
系統呼叫：
分散
／
聚集
I/O（scatter/gather I/O）
讓單一呼叫得以同時對多個緩衝區進行資料的讀取或寫入操作；可用於把不同資料
結構的欄位聚集成單次 I/O 操作。
事件輪詢
（event poll，
簡稱
Epoll）
用於改善第 2 章所提到的
poll()
及
select()
系統呼叫；若有需要從單一執行緒來輪
詢上百個檔案描述器，則可以使用此介面。
記憶體映射
I/O（memory-mapped I/O）
把一個檔案映射至記憶體，讓檔案 I/O 得以透過簡單的記憶體操作來進行；可用於
特定類型的 I/O。
檔案指示
（file advice）
讓一個行程得以提示核心，自己的使用情況；如此可改善 I/O 的效能。
非同步
I/O（asynchronous I/O）
允許一個行程送出 I/O 要求，而不需要等待它們完成；可在不使用執行緒的情況
下，操弄沈重的 I/O 工作量。
本章結束時將討論效能的問題以及核心的 I/O 子系統。
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.