polly poll

The action of the Select () function system invokes the back-end implementation of select and poll, which are used to query whether the device is readable or not, or whether it is in a certain state. If poll is empty, the drive device is considered readable and writable, and the return value is a status mask how to use the Select () function? The interface of the Select () function is primarily based on a

descriptors is relatively small, or when it is relatively large, the stack will be used for storage for the first timeIf (! Stack_pp)Stack_pp = pp = (struct poll_list *) stack_pps;Else {Pp = kmalloc (size, gfp_kernel );If (! Pp)Goto out_fds;}PP-> next = NULL;PP-> Len = num;If (Head = NULL)Head = pp;ElseWalk-> next = pp; Walk = pp;If (copy_from_user (PP-> entries, ufds + NFDs-I,Sizeof (struct pollfd) * num )){Err =-efault;Goto out_fds;}I-= PP-> Len;} // Real

connection is established The descriptor has an error, and returns 1 if the call to the read system calls the reading socket. is considered writable when the following happens: The number of bytes in the socket's send buffer is greater than the Low-water Mark property value of the socket's send buffer and the socket is connected or does not require a connection (such as UDP). Write half connection closed, calling the Write function will produce sigpipe The descriptor h

by select () stores a large number of file descriptors, with the increase in the number of file descriptors, the cost of replication increases linearly. At the same time, because the latency of the network response time makes a large number of TCP connections inactive, but calling select () takes a linear scan of all sockets, so this also wastes some overhead.(2) PollPoll was born in 1986 in System V Release 3, and it does not differ substantially from select in nature, but

Epoll scalability web page Introduction Interface Description Man pages Testing Dphttpd Dphttpd SMP results Dphttpd up results Pipetest Pipetest results Recent comparison results Analysis and conclusions Acknowledgements Introduction Davide libenzi wrote an event poll implementation and described it at the/dev/epoll home page here. his performance testing led to the conclusion that epoll scaled linearly regardless of the loa

multiplexed I/O Model poll () Model Code implementationThe poll () mechanism is similar to the select () mechanism, and is a way to poll multiple descriptors.The difference is that poll () does not have a limit on the number of descriptors.is to poll each descriptor with a s

poll mechanism function: the equivalent of a timer, the time has not yet the resources to wake up the process.The main purpose is: The process is set up for a period of time to wait for resources, if the time to the resource has not arrived, the process immediately from the sleep state wake up no longer waiting. Of course, this is only a situation where resources are useless for the process after that time.The implementation process of the

Transferred from: http://blog.csdn.net/yikai2009/article/details/8653842Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.Directory (?) [-] Select-System call int SELECT-function Function Parameters return value Select-System invoke-how to use 1 adding files to the file descriptor set to be monitored 2 call Select to start monitoring 3 Determine if the file has changed Four

Introduction and implementation of IO multiplexing (SELECT, poll, Epoll)Io multiplexing includes SELECT, pool, Epoll, which are synchronous and not asynchronousI. Introduction of IO multiplexing1. SelectSelect was first seen in 1983 in 4.2BSD, and it is used by a select () system to monitor arrays of multiple file descriptors, and when select () returns, the ready file descriptor in the array is changed by the kernel to the flag bit. Allows the proces

This question interview is often asked, to summarizeSelect, poll, and Epoll are IO multiplexing mechanisms, first listening to multiple file descriptor fd, once an FD is ready, you can read and write the corresponding operation. But the essence of Select, poll, and Epoll are synchronous I/O, they all need to read and write after the read and write event is ready, that is, the read and write process is block

=sizeof(client_address);intCONNFD = Accept (LISTENFD, (structSOCKADDR *) client_address,len);if(CONNFD 0) {cout"Error"Charbuf[1024x768]; Fd_set Readfds; Fd_zero (readfds); while(1) {bzero (buf,1024x768); Fd_set (Connfd,readfds); ret = SELECT (CONNFD +1, readfds,null,null,null);if(Ret 0) {cout"Error"//Interpreting whether readable events occur if(Fd_isset (Connfd,readfds)) {ret = recv (Connfd,buf,sizeof(BUF)-1,0);if(Ret 0) { Break; }coutreturn 0;}Features of

(a) first, introduce several common I/O models and their differencesAs follows: Blocking I/O nonblocking I/O I/O multiplexing (Select and poll) Signal driven I/O (SIGIO) asynchronous I/O (the POSIX aio_functions) ————— The largest feature of the asynchronous IO model is the notification after completion. Blocking or not depends on how the IO Exchange is implemented.Asynchronous blocking is based on the implementation of the Se

The first thing we need to know about select,poll,epoll is The mechanism of IO multiplexing. I/O multiplexing is a mechanism by which multiple descriptors can be monitored, and once a descriptor is ready (usually read-ready or write-ready), the program can be notified of the appropriate read and write operations. But select,poll,epoll are essentially synchronous I/O , because they all need to be responsib

I. About POLLFor the IO multiplexing model, the advantage is that it eliminates the wait for one IO event to be ready, instead of detecting multiple IO data at the same time, when at least one of the waiting events is ready, it will return to tell the user that the process "has data ready, quickly see which one to deal with", For the implementation of IO multiplexing, in addition to the use of the Select function, another function still supports the multiplexed IO model, which is the

Functions of the select () functionThe system calls the back-end Implementation of select and poll, and uses these two system calls to query whether the device can read or write, or whether it is in a certain state. If poll is empty, the driver is considered readable and writable. The returned value is a status mask.How to Use the select () function?The Select () function interface is mainly based on the 'f

The Select,poll,epoll in Linux is a mechanism for IO multiplexing.SelectSelect was first seen in 1983 in 4.2BSD, and it is used by a select () system to monitor arrays of multiple file descriptors, and when select () returns, the ready file descriptor in the array is changed by the kernel to the flag bit. Allows the process to obtain these file descriptors for subsequent read and write operations. Select is currently supported on almost all platforms

The implementation of the function is to read the key information, if the key is not generated, the program sleep in the Read function, using the poll mechanism, you can not exit the program automatically quit. The following program is to read the key information, if there is no key information in the 5000ms, you exit.First the application executes the poll functionThe Sys_poll in kernelDo_sys_pollInit_poll

Introduction to the network I/O multiplexing model select poll epoll First, we need to know that select, poll, and epoll are IO multiplexing mechanisms. I/O multiplexing uses a mechanism to monitor multiple descriptors. Once a descriptor is ready (generally read or write), it can notify the program to perform corresponding read/write operations. However, select, poll