fork | 易学教程

k8s集群环境报错fork: Cannot allocate memory

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在测试环境遇到服务器操作命令提示fork:cannot allocate memory，根据网上资料显示可能是进程数满了由于查看进程数等命令也无效，直接操作修改进程数命令：修改最大进程数后系统恢复 echo 1000000 > /proc/sys/kernel/pid_max 永久生效 echo "kernel.pid_max=1000000 " >> /etc/sysctl.conf sysctl -p 问题解决！来源： CSDN 作者： ST_君华链接： https://blog.csdn.net/Wuli_SmBug/article/details/103767234

Pass the value from child to parent process

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问题 I have this code that is supposed to create three child process' and each will perform a small mathematical operation. Then, the parent is supposed to use the results from all the child process' and get a final answer but I can't find a way to actually read the result from the child in the parent. Is there a way to do this? #include <stdio.h> #include <unistd.h> #include <stdlib.h> int main(void) { int pid1, pid2, pid3, status; int a=1, b=2, c=5, d=4, e=6, f=3, g; int t1, t2, t3; printf(

multicore and data.table in R

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问题 I am attempting to use multicore function parallel with data.table and am unable to quite come up with the right way to do this. Code: require(multicore) require(data.table) dtb = data.table(a=1:10, b=1:2) x = dtb[,parallel(a+1),by=b] > x b pid fd 1: 1 12243 3 2: 1 12243 6 3: 2 12247 4 4: 2 12247 8 I would like to call collect() on this but these are no longer parallel objects. How should one do this? 回答1: I think this is along the lines of what you want: collect(dtb[, list(jobs = list

What Happens When I Call fork() in Unix?

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问题 I've tried to look this up, but I'm struggling a bit to understand the relation between the Parent Process and the Child Process immediately after I call fork(). Are they completely separate processes, only associated by the id/parent id? Or do they share memory? For example the 'code' section of each process - is that duplicated so that each process has it's own identical copy, or is that 'shared' in some way so that only one exists? I hope that makes sense. In the name of full disclosure

create a process tree in C

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问题 How would I approach creating a process hierarchy that would look like a balanced ternary tree of depth N? ... meaning each process has 3 children so there would be (3^N-1)/2 processes in a tree of depth N. To create the new processes, I only want to use fork(). This is what I have so far but I don't think it works because I don't deal with process IDs and also I really don't think I should do this recursively: void createTernaryTree(int n) { if((n-1) == 0) return; else { int x; for(x=0; x<3;

address space after fork call

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问题 When fork() sys call is executed by the process, a child process generated from it. All the codes following the fork() call is copied to the new physical pages of memory i.e frames. I am not able to visualize the virtual memory part of the child process.because in the following code the address of char variable is same in child as well as parent. #include <stdio.h> #include <sys/types.h> int main(void) { pid_t pid; char y='Y'; char *ptr; ptr=&y; pid = fork(); if (pid == 0) { y='Z'; printf(" *

CGI,FastCGI,PHP-FPM

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CGI（Common Gateway Interface） CGI 是Web 服务器运行时外部程序的规范,按CGI 编写的程序可以扩展服务器功能。CGI 应用程序能与浏览器进行交互,还可通过数据库API 与数据库服务器等外部数据源进行通信,从数据库服务器中获取数据。格式化为HTML文档后，发送给浏览器，也可以将从浏览器获得的数据放到数据库中。几乎所有服务器都支持CGI,可用任何语言编写CGI,包括流行的C、C ++、VB 和Delphi 等。CGI 分为标准CGI 和间接CGI两种。标准CGI 使用命令行参数或环境变量表示服务器的详细请求，服务器与浏览器通信采用标准输入输出方式。间接CGI 又称缓冲CGI,在CGI 程序和CGI 接口之间插入一个缓冲程序，缓冲程序与CGI 接口间用标准输入输出进行通信 FastCGI FastCGI像是一个常驻(long-live)型的CGI，它可以一直执行着，只要激活后，不会每次都要花费时间去fork一次(这是CGI最为人诟病的fork-and-execute 模式)。它还支持分布式的运算, 即 FastCGI 程序可以在网站服务器以外的主机上执行并且接受来自其它网站服务器来的请求。 FastCGI是语言无关的、可伸缩架构的CGI开放扩展，其主要行为是将CGI解释器进程保持在内存中并因此获得较高的性能。众所周知

linux-进程概念

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1.冯诺依曼体系体系的构成：运算器，存储器(RAM 和 ROM)，控制器，输入设备，输出设备思想： 1.数据和程序是以二进制代码的形式放在存储器中，存放的位置由地址指定，地址码也是二进制的。 2.控制器是根据存放在存储器中的指令序列即程序来工作的，并由一个程序计数器(指令地址计数器)控制指令执行。控制器具有判断能力，能根据计算结果选择不同的动作流程。注意： ;a 这里的存储器指的是内存 b 不考虑缓存情况，这里的CPU能且只能对内存进行读写，不能访问外设(输入或输出设备) c 外设(输入或输出设备)要输入或者输出数据，也只能写入内存或者从内存中读取。 d 所有设备都只能直接和内存打交道。 2.操作系统操作系统是一个软件，是管理计算机硬件与软件资源的计算机程序，同时也是计算机系统的内核与基石。操作系统需要处理如管理与配置内存、决定系统资源供需的优先次序、控制输入设备与输出设备、操作网络与管理文件系统等基本事务。操作系统也提供一个让用户与系统交互的操作界面。操作系统的构成操作系统内核(进程管理，内存管理，文件管理，驱动管理)，其他应用(函数库，shell程序等等) 系统调用：操作系统提供的函数，称之为系统调用函数库函数：系统在功能调用的使用上，功能比较基础，对用户的要求相对比较高，然后一些有心的开发者(大佬们)

How can I run a program in the background (non blocking) with php?

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问题 I want to run a shell script in php, but this shell script takes a long time to execute (it has sleep in it), I don't want the web server to block when executing this script. I tried exec() and shell_exec() in php but the server stops until the shell script finishes! I thought of doing fork in the shell script itself but I don't know how to do that. I just want the php script to call this shell script and continue working, I'm not waiting any result from the script. I tried running the shell

How does copy-on-write work in fork()?

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问题 I want to know how copy-on-write happens in fork(). Assuming we have a process A that has a dynamical int array: int *array = malloc(1000000*sizeof(int)); Elements in array are initialized to some meaningful values. Then, we use fork() to create a child process, namely B. B will iterate the array and do some calculations: for(a in array){ a = a+1; } I know B will not copy the entire array immediately, but when does the child B allocate memory for array? during fork()? Does it allocate the