The article explains how storage media speed, kernel and user mode separation, and context‑switch overhead affect I/O performance, then details DMA, zero‑copy methods such as mmap + write and sendfile, the role of PageCache, and best practices like async and direct I/O for large‑file transfers.
A nostalgic narrative explains how low‑level hardware control led to the invention of system calls, kernel/user modes, and ultimately the operating system concept, illustrating the transition from direct hardware manipulation to abstracted library functions.
In the 1950s programmers wrote directly to hardware, but the fragility of hard‑coded memory and I/O led to the invention of a privileged “expert” kernel mode and a restricted “novice” user mode, with a special instruction to switch, forming the basis of modern system calls and operating system protection.
The article compares user‑mode and kernel‑mode GPU virtualization, detailing their layered architectures, how they intercept APIs, the advantages such as openness, isolation, and unified memory, and the drawbacks including API complexity, kernel intrusion, legal risks, and cross‑process limitations.
This article explains the performance hierarchy of storage media, the distinction between kernel and user modes, how data moves between them, and why excessive context switches hurt I/O, then introduces DMA, zero‑copy, PageCache, mmap + write, sendfile, and tuning tips to dramatically improve Linux I/O efficiency.
This article explains the basic concepts of operating systems, covering their role as a hardware abstraction layer, the distinction between kernel and user modes, and how OS resource management (time‑sharing and space‑sharing) enables multiple programs to run safely and efficiently.
