Tips on Profile 先说几个小坑点： 默认情况下，Golang Profile 取样的频率为 100Hz，意味着每 10ms 才会取样一次，所以程序运行时间少于 10ms 肯定不会被取样 但是我们可以通过 runtime.SetCPUProfileRate() 重新设置值，重新进行调试，比如将采样率设置为 1000，每 1ms 就会取样一次，但是这样对性能的开销很大，Golang 官方建议这个值不要设置在 200 以上 其实最好的还是让程序多运行一段时间，比如 1s 左右，个人测试即使将采样率调高，如果一个程序只运行 10ms 左右，采样的结果也大概率为空 在正确位置设置上述语句后，程序提示 “runtime: cannot set cpu profile rate until previous profile has finished."，这句错误提示简直不明不白的，我第一次看到这个错误提示还以为就是字面意思：系统中可能存在正在运行的 profile 程序 查资料后发现，runtime.SetCPUProfileRate() 是一种比较 Hack 的做法，所以该错误提示可以忽略 在程序运行时，直接通过 kill 命令结束程序的话，最后生成的 profile 为空（？），最好使用下面的这个模式： sigs := make(chan os.Signal, 1) signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM) server := NewServer(port, connMap) go server.Run() <-sigs Log.Info("Shutting down server") 通过 signal.Notify 来拦截 kill 的信号，保证程序能够正常结束，profile 文件不为空 How to Profile if pprofFlag { // runtime.SetCPUProfileRate(1000) cpuFile, err := os.Create("executor_profile.prof") if err != nil { fmt.Println("无法创建 CPU profile 文件:", err) return } defer cpuFile.Close() // 开始 CPU profile if err := pprof.StartCPUProfile(cpuFile); err != nil { fmt.Println("无法启动 CPU profile:", err) return } defer pprof.StopCPUProfile() } 注意这段代码只能放在 main 函数中，否则 defer 语句的语义会有影响 How to Read Profile Results 命令行 (pprof) top 10 Showing nodes accounting for 40ms, 100% of 40ms total Showing top 10 nodes out of 26 flat flat% sum% cum cum% 10ms 25.00% 25.00% 10ms 25.00% os.(*File).checkValid (inline) 10ms 25.00% 50.00% 10ms 25.00% runtime.(*mheap).allocSpan 10ms 25.00% 75.00% 10ms 25.00% runtime.(*profBuf).read 10ms 25.00% 100% 10ms 25.00% runtime.startm 0 0% 100% 10ms 25.00% log.(*Logger).Output 0 0% 100% 10ms 25.00% log.Println 0 0% 100% 10ms 25.00% main.main.func1 0 0% 100% 10ms 25.00% os.(*File).Write 0 0% 100% 10ms 25.00% runtime.(*mcache).nextFree 0 0% 100% 10ms 25.00% runtime.(*mcache).refill flat：该函数本身直接消耗的时间。比如，flat = 10ms 表示这个函数自身消耗了 10 毫秒的 CPU 时间，而不是它调用的其他函数所消耗的时间。 ...

Job Control Signals can do other things beyond killing a process. For instance, SIGSTOP pauses a process. In the terminal, typing Ctrl-Z will prompt the shell to send a SIGTSTP signal, short for Terminal Stop. We can then continue the paused job in the foreground or in the background using fg or bg. One more thing to know is that the & suffix in a command will run the command in the background, giving you the prompt back. ...

# journalctl run remotely, grep run locally ssh myserver journalctl | grep sshd # both commands run remotely ssh myserver "journalctl | grep sshd" sed sed (Stream Editor) is a powerful command-line tool in Unix/Linux that is used for parsing and transforming text, typically used for finding, replacing, or deleting content in a file or input stream. Common sed Commands: Substitution (s): sed 's/pattern/replacement/' file s: The substitution command. pattern: The string or pattern to search for. replacement: The string to replace the pattern with. Example: ...

Shell Tools and Scripting Shell Scripting To assign variables in bash, use the syntax foo=bar and access the value of the variable with $foo. Note that foo = bar will not work since it is interpreted as calling the foo program with arguments = and bar. bash uses a variety of special variables to refer to arguments, error codes, and other relevant variables: $0 - Name of the script $1 to $9 - Arguments to the script. $1 is the first argument and so on. $@ - All the arguments $# - Number of arguments $? - Return code of the previous command $$ - Process identification number (PID) for the current script !! - Entire last command, including arguments. A common pattern is to execute a command only for it to fail due to missing permissions; you can quickly re-execute the command with sudo by doing sudo !! $_ - Last argument from the last command. If you are in an interactive shell, you can also quickly get this value by typing Esc followed by . or Alt+. Exit codes can be used to conditionally execute commands using && (and operator) and || (or operator). ...

The shell How does the shell know how to find the date or echo programs? The shell is a programming environment, just like Python, and so it has variables, conditionals, loops, and functions. If the shell is asked to execute a command that doesn’t match one of its programming keywords, it consults an environment variable called $PATH that lists which directories the shell should search for programs when it is given a command ...