AI代码解释 #include<unistd.h>#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>main(){int fd,size;char s[]=”Linux Programmer!\n”,buffer[80];fd=open(“/tmp/temp”,O_WRONLY|O_CREAT);write(fd,s,sizeof(s));close(fd);fd=open(“/tmp/temp”,O_RDONLY);size=read(fd,bu...
// 使用更大的缓冲区 char large_buffer[4096]; write(fd, large_buffer, sizeof(large_buffer)); 示例代码 以下是一个简单的字符设备驱动示例,展示了如何实现write函数: 代码语言:txt 复制 #include <linux/module.h> #include <linux/fs.h> #include <linux/cdev.h> static ssize_t my_write(struct ...
一、lfs mode bufferd write 写操作分为bufferd write和direct write,两种write处理流程有一些区别,这里只讨论lfs模式下bufferd write的写流程。 bufferd write:数据在page cache里缓存一段时间后,worker_thread线程唤醒名称为“writeback”的workqueu,将数据写入存储设备。 ps命令看到的内核线程[kworker/u2:1-wr],...
int fd,size; char s [ ]=”Linux Programmer!\n”,buffer[80]; fd=open(“/tmp/temp”,O_WRONLY|O_CREAT); write(fd,s,sizeof(s)); close(fd); fd=open(“/tmp/temp”,O_RDONLY); size=read(fd,buffer,sizeof(buffer)); close(fd); printf(“%s”,buffer); } read 函数定义: ssize_t ...
文章从概念到代码由浅入深、层层递进,虽然是围绕管道读写性能优化展开,但相信高性能应用程序或Linux内核的相关开发人员都会从中受益匪浅。 本文将对一个通过管道写入和读取数据的测试程序进行反复优化,以此研究 Unix 管道在 Linux 中的实现方式。 我们从一个吞吐量约为 3.5GiB/s 的简单程序开始,并逐步将其性能提升 ...
这里给出了一个不怎么标准的驱动,定义了一个结构体 struct dev,其中buffer成员模拟驱动的寄存器。由wr,rd作为读写指针,len作为缓存buffer的长度。具体步骤如下: 1. 定义 init 函数,exit函数,这是在 insmod,rmmod时候调用的。 2. 定义驱动打开函数open,这是在用户态打开设备时候调用的。
#include#include#include#includemain(){intfd,size;chars[]=”Linux Programmer!\n”,buffer[80];fd=open(“/tmp/temp”,O_WRONLY|O_CREAT);write(fd,s,sizeof(s));close(fd);fd=open(“/tmp/temp”,O_RDONLY);size=read(fd,buffer,sizeof(buffer));close(fd);printf(“%s”,buffer);} ...
The operating system transfers the write buffer to the disk controller (data is in the disk cache). The disk controller actually writes the data into a physical media (a magnetic disk, a Nand chip, …). 总结: 当我们到第3 步, 也就是write 操作系统返回的时候, 可以保证的是如果process 挂...
RWF_NOWAIT(since Linux 4.14) Do not wait for data which is not immediately available. If this flag is specified, thepreadv2() system call will return instantly if it would have to read data from the backing storage or wait for a lock. If some data was successfully read, it will return...
edited by filimonov 2019.01.03 15:31:07.561639 [ 22565132 ] {} <Error> virtual DB::WriteBufferFromOStream::~WriteBufferFromOStream(): Code: 24, e.displayText() = DB::Exception: Cannot write to ostream at offset 1071166, e.what() = DB::Exception, Stack trace: 0. clickhouse-server(Stack...