Slide 充斥着大量的谬误与个人的随意理解: sched_ext机制研究
简介 <The extensible scheduler class [LWN.net]>
BPF背后的核心思想是, 它允许程序在运行时从用户空间加载到内核中; 与现在的Linux系统相比, 使用BPF进行调度有可能实现明显不同的调度行为. 那么, 为什么现在要提出BPF机制呢? 为了期待一场长时间的讨论, 补丁系列的封面信详细描述了这项工作背后的动机. 简而言之, 该论点认为, 在BPF中编写调度策略的能力大大降低了试验新调度方法的难度. 由于引入了完全公平调度器CFS, 我们的工作负载及其运行的系统都变得更加复杂. 要开发适合当前系统的调度算法, 需要进行试验. BPF调度类允许以一种安全的方式进行实验, 甚至不需要重新启动测试机器. bpf编写的调度器还可以提高可能不值得在主线内核中支持的小众工作负载的性能, 这些工作负载更容易部署到大量系统中.
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正确的办法! du -d 1 -h | sort -hr duu du 指令无法以可读的形式按照大小排序, du -d 1 -h | sort -nr并不正确, 因而写一个简单的脚本进行实现.
rust 1use std::env; 2 3fn main() { 4 let args: Vec<String> = env::args().collect(); 5 assert!(args.len() >= 2); 6 7 if args[1].len() > 18 { 8 println!("Number too large"); 9 return; 10 } 11 12 for c in args[1].chars() { 13 if !c.is_digit(10) { 14 println!("Invalid number"); 15 return; 16 } 17 } 18 19 let nr_bytes = args[1].parse::<u64>().unwrap(); 20 /* KB -> MB -> GB */ 21 22 let mut level: usize = 0; 23 let mut tmp = nr_bytes; 24 while tmp > 0 { 25 tmp /= 1024; 26 if tmp > 0 { 27 level += 1; 28 } 29 } 30 31 // du指令默认的单位是KB! 32 let levels = ["KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"]; 33 print!("{:>.2}\t{}\t", nr_bytes as f64 / u64::pow(1024, level as u32) as f64, levels[level]); 34} 再用awk处理一下du的第一列输出.
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参考文档 More Control and Package Management using Package Users (v1.4)
工具包: more_control_helpers
Shell 编程 特殊变量 $开头的一些特殊变量:
Text 1Special Parameters 2 The shell treats several parameters specially. These parameters may only 3 be referenced; assignment to them is not allowed. 4 * Expands to the positional parameters, starting from one. When the 5 expansion is not within double quotes, each positional parameter expands to 6 a separate word. In contexts where it is performed, those words are 7 subject to further word splitting and pathname expansion. When the 8 expansion occurs within double quotes, it expands to a single word with the 9 value of each parameter separated by the first character of the IFS 10 special variable. That is, "$*" is equivalent to "$1c$2c...", where c 11 is the first character of the value of the IFS variable. If IFS is unset, 12 the parameters are separated by spaces. If IFS is null, the parameters are 13 joined without in‐ tervening separators. 14 @ Expands to the positional parameters, starting from one. In 15 contexts where word splitting is performed, this expands each positional 16 parameter to a separate word; if not within double quotes, these words are 17 subject to word splitting. In contexts where word splitting is not 18 performed, this expands to a single word with each po‐ sitional parameter 19 separated by a space. When the expansion occurs within double quotes, 20 each parameter ex‐ pands to a separate word. That is, "$@" is 21 equivalent to "$1" "$2" ... If the double-quoted expansion occurs within a 22 word, the expansion of the first parameter is joined with the beginning 23 part of the original word, and the expansion of the last parameter is 24 joined with the last part of the original word. When there are no posi‐ 25 tional parameters, "$@" and $@ expand to nothing (i.e., they are removed). 26 # Expands to the number of positional parameters in decimal. 27 ? Expands to the exit status of the most recently executed foreground 28 pipeline. 29 - Expands to the current option flags as specified upon invocation, by 30 the set builtin command, or those set by the shell itself (such as the -i 31 option). 32 $ Expands to the process ID of the shell. In a () subshell, it 33 expands to the process ID of the current shell, not the subshell. 34 ! Expands to the process ID of the job most recently placed into the 35 background, whether executed as an asynchronous command or using the bg 36 builtin (see JOB CONTROL below). 37 0 Expands to the name of the shell or shell script. This is set 38 at shell initialization. If bash is invoked with a file of commands, $0 is 39 set to the name of that file. If bash is started with the -c option, then 40 $0 is set to the first argument after the string to be executed, if 41 one is present. Otherwise, it is set to the filename used to invoke bash, 42 as given by argument zero. type命令 默认的man好像显示的不是bash command的type, 因而去别处找了一份mannual:
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Linux
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