/en/authors/kirin/ Recent content in Kirin on Kirin's Backspace Hugo en © {year} Kirin Thu, 10 Oct 2024 23:50:00 +0800 /en/_deprecated_posts/os-review/ Sat, 27 May 2023 21:29:00 +0800 /en/_deprecated_posts/os-review/ Ch6, 7 Process Synchronization What is race condition? Ch6,7 Page 4 Race condition: several processes access and manipulate the same data concurrently outcome depends on which order each access takes place. 竞态条件（race condition）：多个进程并发访问和操作统一数据并且执行结果与特定 /en/_deprecated_posts/os-note-ch5-cpu-scheduling/ Wed, 29 Mar 2023 09:50:00 +0800 /en/_deprecated_posts/os-note-ch5-cpu-scheduling/ Basic Concepts Purpose of multiprogramming: maximum CPU utilization CPU–I/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait CPU burst followed by I/O burst CPU burst distribution is of main concern: a large number of short CPU bursts and a small number of long CPU bursts. Operation Type Load store, add store, read from file CPU burst Wait for I/O I/O burst Store increment /en/_deprecated_posts/os-note-ch4-threads/ Tue, 28 Mar 2023 21:38:00 +0800 /en/_deprecated_posts/os-note-ch4-threads/ Overview Motivation Behind Threads Multiple tasks with the application can be implemented by separate threads (Scalability, Responsiveness ) Update display Fetch data Spell checking Answer a network request Process creation is heavy-weight while thread creation is light- weight (economy) Threads run within the application/process (Resource Sharing) Can simplify code, increase efficiency Most modern applications are multithreaded Kernels are generally multithreaded Single and Multithreaded Processes Multithreaded Server Architecture Benefits Responsiveness – may allow continued execution if /en/_deprecated_posts/os-note-ch3-processes/ Mon, 27 Mar 2023 09:00:00 +0800 /en/_deprecated_posts/os-note-ch3-processes/ Process Concept Process a program in execution in memory execution must progress in sequential fashion There can be several processes for one program Consider multiple users executing the same program Memory [Process (active)] A | Mouse click or command input | Loader loads program | Disk [Program: Executable file <= Object file <= Source file (passive)] ELF Object File Format: ELF (Executable and Linkable Format , Generic name: ELF binaries) A process includes multiple parts /en/_deprecated_posts/os-note-ch2-operating-system-structures/ Sun, 26 Mar 2023 20:43:00 +0800 /en/_deprecated_posts/os-note-ch2-operating-system-structures/ Operating System Services Operating systems provide an environment that offer services to programs and users Functions to the user User interface (UI) Command-Line Interface (CLI), Graphics User Interface (GUI), touch-screen, batch processing (批处理) Program execution Load a program into memory Run a program, and then end execution. I/O operations File-system manipulation Read-write Communications Process exchange information Error detection Handle possible errors (from hardware or software) Functions for the efficient operations Resource /en/_deprecated_posts/os-note-ch1-introduction/ Sun, 26 Mar 2023 16:33:00 +0800 /en/_deprecated_posts/os-note-ch1-introduction/ Computer-System Architecture and Organization I/O Devices: except CPU and memory I/O devices and the CPU can work concurrently(同时) CPU and Memory in Computer Single processor Multiple processors Dual core Non-Uniform Memory Access System (NUMA) Device driver (software) inside the kernel knows how to talk and manage the device provides uniform interface between controller and kernel Each device controller informs CPU /en/posts/h248-calling/ Mon, 09 Jan 2023 21:24:00 +0800 /en/posts/h248-calling/ Background This is my first blog post of 2023. I feel embarrassed that I haven’t produced many meaningful or valuable articles in the past two years. However, the posts I recorded in my blog were born from urgent problems or ideas that I resolved. In fact, I solved this problem back in mid-last year, but I never found the time to document my exploration process—so here it is now. At the beginning of last year, I had just completed my article “Replacing My HN8145V Optical Modem with Huawei MA5671A. /en/posts/dkey-token-to-standard-totp/ Fri, 27 May 2022 10:00:00 +0800 /en/posts/dkey-token-to-standard-totp/ What is TOTP? TOTP, short for Time-based One-Time Password, is a form of 2FA (two-factor authentication) that calculates a one-time password based on a pre-shared key and the current time. It generates dynamic 6-digit or 8-digit codes from a fixed secret. Both the user and the server hold the same secret, ideally only shared between them. This secret is a string of binary data that is base32 encoded for easier transmission, with the last = removed. /en/posts/solve-ipv6-issue-in-my-dorm/ Thu, 19 May 2022 10:00:00 +0800 /en/posts/solve-ipv6-issue-in-my-dorm/ Background My broadband ISP in my dormitory is China Unicom, FTTB. It is terrible that it has only 100Mbps connectivity (Fast Ethernet). But the most horrible thing is that the BRAS only assigned the IPv6 address by SLAAC, even can not assign PD prefix to my router. CU is the only ISP that provides PPPoE + IPv6 + public IPv4 in our university. Because of this, I didn’t change my mind to migrate my ISP /en/posts/vlan-iptv/ Sat, 05 Feb 2022 17:09:00 +0800 /en/posts/vlan-iptv/ Background In a new network environment, the wireless AP is located in a metal weak current box, resulting in poor signal strength. The network port in the living room is connected to the IPTV interface of the optical modem with only one line, which cannot carry internet services. This is clearly a problem caused by not adequately planning during the renovation, leaving only one line. How can we move the wireless access point from the weak current box to the living room without running additional cables while ensuring that the normal internet needs of the entire house are not affected?