fork

Perl - Communicating with a fork/exec'ed process

由 房东的猫 提交于 2020-01-16 07:08:21
问题 I'm designing a server that will initialize by fork / exec 'ing four "managers" (themselves server processes) and will then accept connections from clients, fork / exec 'ing "slaves" to communicate with the clients. During their lifetimes, the slaves will establish connections with the managers and send them work requests. My question is about starting up the managers. Each one may take some time to initialize (minutes) and I don't want the master server to proceed to accept clients until

Perl fork queue for n-Core processor

由 时光总嘲笑我的痴心妄想 提交于 2020-01-15 23:03:07
问题 I am writing an application similar to what was suggested here. Essentially, I am using Perl to manage the execution of multiple CPU intensive processes in parallel via fork and wait. However, I am running on a 4-core machine, and I have many more processes, all with very dissimilar expected run-times which aren't known a priori. Ultimately, it would take more effort to estimate the run times and gang them appropriately, than to simply utilize a queue system for each core. Ultimately I want

Linux环境变量编程--进程创建

由 对着背影说爱祢 提交于 2020-01-15 15:16:21
进程创建 1.进程号获取 2.fork()函数创建子进程 2.1 父进程和子进程执行顺序？是否会阻塞？ 2.2 进程数据共享么？ 2.3 子进程何时执行？ 2.4 子进程{}之后的代码是谁的？ 3. vfork()函数创建子进程 3.1 父子进程执行顺序？ 3.2 父子进程何时执行？ 3.3 子进程{}之后的代码是谁的？ 3.4 进程数据共享么？ 1.进程号获取 pid_t getpid(void); 返回当前进程的进程号 pid_t getppid(void); 返回当前的进程的父进程 2.fork()函数创建子进程 fork：目的是在当前进程下创建一个子进程. fork调用的一个奇妙之处就是它仅仅被调用一次，却能够返回两次. 它可能有三种不同的返回值： 1）在父进程中，fork返回新创建子进程的进程ID； 2）在子进程中，fork返回0； 3）如果出现错误，fork返回一个负值； 在fork函数执行完毕后，如果创建新进程成功，则出现两个进程，一个是子进程，一个是父进程．在子进程中fork函数返回0，在父进程中，fork返回新创建子进程的进程ID大于０。我们可以通过fork返回的值来判断当前进程是子进程还是父进程。 0 表示的是子进程的进程号，那么这个fork是父进程执行的结果 0 表示的是,这是由子进程执行的结果 -1 父进程创建子进程失败，此时不会有子进程创建 2.1

Call system() inside forked (child) process, when parent process has many threads, sockets and IPC

由 五迷三道 提交于 2020-01-15 15:08:12
问题 I have a program that have many threads. Some threads are TCP servers... Each server fires new threads to handle any new connections. Inside one of the threads that handles a single client, I call fork(). The child process calls setpgid() (to create a new group) and then system() (the function of C/C++ standard library). The parent process keeps taking naps (usleep() function) and checking a time limit. If the time limit is exceeded before child process returns from system(), the parent

Content written before fork() present in output twice

由 a 夏天 提交于 2020-01-15 11:24:53
问题 I wrote the following C code: #include<stdio.h> int main(){ printf("A"); if(fork() == 0){ printf("B"); } else{ printf("C"); } } The output I got is: ACAB I expected this code to print A only once. Can anyone explain this output? 回答1: Your error is not flushing the buffers before fork -ing, thus both processes will write it. Add this before fork() : fflush(0); // Flush all output-streams 回答2: The 'A' is stored in a buffer and flushed by both processes when they exit. 来源： https://stackoverflow

Content written before fork() present in output twice

由 |▌冷眼眸甩不掉的悲伤 提交于 2020-01-15 11:24:30
问题 I wrote the following C code: #include<stdio.h> int main(){ printf("A"); if(fork() == 0){ printf("B"); } else{ printf("C"); } } The output I got is: ACAB I expected this code to print A only once. Can anyone explain this output? 回答1: Your error is not flushing the buffers before fork -ing, thus both processes will write it. Add this before fork() : fflush(0); // Flush all output-streams 回答2: The 'A' is stored in a buffer and flushed by both processes when they exit. 来源： https://stackoverflow

UVM phase机制（三）objection机制

由 隐身守侯 提交于 2020-01-15 08:23:01
在上一篇博客UVM phase机制（二）中，我们有介绍到run_phase以及12个run_time_phase是如何运转起来的，但是留了一个小问题就是objection，想要run必须raise_objection，要想结束run必须drop_objection。下面我们详细分析一下为什么会这样 在运行到run_node的时候，是这样一个执行结构， fork fork env.run_phase(uvm_phase phase); join_none fork uvm_test_top.run_phase(uvm_phase phase); join_none fork top.run_phase(uvm_phase phase); join_none join_none 但是，最终完整的执行结构是 fork fork env.run_phase(uvm_phase phase); join_none fork uvm_test_top.run_phase(uvm_phase phase); join_none fork top.run_phase(uvm_phase phase); join_none join_none #0; fork begin fork process(0);//junp process(1);//objection process(2);/

How to know the execution time in linux

由 自作多情 提交于 2020-01-15 06:19:26
问题 Suppose that I have three script(a.sh b.sh c.sh) to be launched in a script called launcher.sh: first=`date +%s` ./a.sh & ./b.sh & ./c.sh & final=`date +%s` executionTime=`echo "scale=3;($final - $first)/3600" | bc` echo $executionTime I know above script won't work because launcher.sh will finish immediately after launching a.sh, b.sh and c.sh. Launching a.sh, b.sh and c.sh without "&" is wasting time because they don't have to wait for each other. Suppose that the execution time for them

How to know the execution time in linux

由 ☆樱花仙子☆ 提交于 2020-01-15 06:19:09
问题 Suppose that I have three script(a.sh b.sh c.sh) to be launched in a script called launcher.sh: first=`date +%s` ./a.sh & ./b.sh & ./c.sh & final=`date +%s` executionTime=`echo "scale=3;($final - $first)/3600" | bc` echo $executionTime I know above script won't work because launcher.sh will finish immediately after launching a.sh, b.sh and c.sh. Launching a.sh, b.sh and c.sh without "&" is wasting time because they don't have to wait for each other. Suppose that the execution time for them

解决 Redis 只读不可写的问题

由 ╄→гoц情女王★ 提交于 2020-01-15 02:29:53
本文转载： https://blog.csdn.net/han_cui/article/details/54767208?tdsourcetag=s_pcqq_aiomsg 解决 Redis 只读不可写的问题 在 Redis 终端上进行读写操作，发现只读不可写，GET 操作是正常的，SET 操作提示错误：(error)MISCONF Redis is configured to save RDB snapshots,but is currently not able to persist on disk. Commands that may modify the data set are disabled. 如图所示： 原因： Redis 在保存数据到硬盘时为了避免主进程假死，需要 Fork 一份主进程，然后在 Fork 进程内完成数据保存到硬盘的操作，如果主进程使用了 4 GB 的内存，Fork 子进程的时候需要额外的 4 GB，此时内存就不够了，Fork 失败，进而数据保存硬盘也失败了。 Linux 内核会根据参数 vm.overcommit_memory 参数的设置决定是否放行。 如果 vm.overcommit_memory = 1，直接放行。 vm.overcommit_memory = 0：则比较此次请求分配的虚拟内存大小和系统当前空闲的物理内存加上swap
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