The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of Unix-like systems. It has been made popular by its use in Linux distributions, but it is used by other Unix-like systems as well. It is maintained by the Linux Foundation. The latest version is 3.0, released on 3 June 2015. procfs (5) $ /proc/cpuinfo $ /proc/kmsg $ /proc/mounts $ /proc/timer_stats $ /proc/sched_debug $ /proc/timer_list $ /proc/diskdump

relativing file/directory $ repository/.git/ $ .gitignore $ ~/.gitconfig $ source /usr/share/bash-completion/completions/git basic git init --bare git fetch <remote> git pull = git fetch + git merge git add -patch <file>

GDBserver gdbserver <ip>:<port> --attach <pid> gdbserver <ip>:<port> <program> GDB si (execute single instruction) stepi next step list <line|function> disas <function>

Memory hierarchy Cache line is the unit of data transfer between CPU and main memory. The cache line of your PC is most likely 64 bytes, meaning that the main memory is divided into blocks of 64 bytes, and whenever you request a byte, you are also fetching its cache line neighbours regardless whether your want it or not. Fetching a cache line is like grabbing a 6-pack. Eviction policy is the method for deciding which data to retain in the cache. In CPUs, it is controlled by hardware, not software. For simplicity, programmer can assume that least recently used (LRU) policy is used, which just evicts the item that hasn’t been used for the longest amount of time. This is like preferring beer with later expiration dates. Eytzinger Binary Search Multi-Programming In the early days of computing, CPU time was expensive, and peripherals were very slow. When the computer ran a program that needed access to a peripheral, the central processing unit (CPU) would have to stop executing program instructions while the peripheral processed the data. This was usually very inefficient. The first computer using a multiprogramming system was the British Leo III owned by J. Lyons and Co. During batch processing, several different programs were loaded in the computer memory, and the first one began to run. When the first program reached an instruction waiting for a peripheral, the context of this program was stored away, and the second program in memory was given a chance to run. The process continued until all programs finished running.

format of Executable and Linking Format (ELF) files image image .dynsym This table contains a subset of the symbols from the .symtab table that are needed to support dynamic linking. This symbol table is allocable, and is therefore available in the memory image of the process. This section holds the dynamic linking symbol table. .symtab This symbol table contains every symbol that describes the associated ELF file. This symbol table is typically non-allocable, and is therefore not available in the memory image of the process.

normal mode insert mode vim.rc set cursorline set ai set bg=light set shiftwidth=8 set tabstop=8 set mouse=a

hackmd-github-sync-badge visualising alorighm Data structure Array Linking list Stak Heap Max heap

Introduction Years Technical 2004 kprobes/kretprobes 2005 systemtap

EasyMesh R1 R1是定義一個基本的共通性的Mesh網路框架，其他主要功能有： 診斷功能，能監控接入點和無線用戶端兩者的連線能力、回程(Backhaul)或>前傳(Fronthaul)的效能及信標(Beacon)報告 引導功能，無線AP會時時地進行效能比對及監控連線品質，將裝置引導到較好的無線環境。 頻段及訊號強度的配置優化 透過訊息交換來強化引導功能 EasyMesh R2

Introduction Mesh Wi-Fi 最主要跟基本的訴求就是提供零死角、好網路品質的無線網路環境。Mesh Wi-Fi 的 Network Topology 如下圖右一。 End Node 為 Wi-Fi AP，此種拓樸可以增加無線網路覆蓋率與 Wi-Fi 訊號。Client 可視當下情況選擇合適的 AP 或 Band 使用。例如，當 STA 從 A 地移動 B 地，STA 可以自動從原本連線的 AP，換成附近的 AP;STA 從原本 AP 的5G Wireless 連線，切換成 2.4G wirless 連線，確保連線品質不會斷線， 接下來，我們介紹 Mesh Wi-Fi 中，會使用到的三種技術 IEEE 802.11k、 802.11v、802.11r。 802.11k (Radio Resource Management) 802.11k enable STAs to understand the radio environment in which they exist.