poll code

file descriptors whose revents is not 0 in the struct is returned. The pollfd structure monitoring event types are as follows: #define POLLIN 0x0001#define POLLPRI 0x0002#define POLLOUT 0x0004#define POLLERR 0x0008#define POLLHUP 0x0010#define POLLNVAL 0x0020#define POLLRDNORM 0x0040#define POLLRDBAND 0x0080#define POLLWRNORM 0x0100#define POLLWRBAND 0x0200#define POLLMSG 0x0400#define POLLREMOVE 0x1000#define POLLRDHUP 0x2000 The above is the value range of the events event mask. Pollin | poll

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

Poll is similar to select, which iterates through the descriptor to see if a descriptor is ready. Returns the number of ready file descriptors if one is available. The poll function is as follows:#include int poll (struct POLLFD *fdarray, unsigned long nfds, int timeout)The first argument points to a pointer to the first element of the structure array, each of wh

To thoroughly understand poll or understand the following code, please refer to the "Linux network programming--i/o multiplexing poll function"Code:1#include string.h>2#include 3#include 4#include 5#include Select.h>6#include 7#include 8#include inch.h>9#include Ten#include One#include A #defineOpen_max 100 - - in

readiness notification method.Epoll can support both horizontal and edge triggering (edgetriggered, which only tells the process which file descriptor has just become ready, it only says it again, and if we do not take action then it will not be told again, this way is called edge triggering ), The performance of edge triggering is theoretically higher, but the code implementation is quite complex.Epoll also only informs those file descriptors that a

1, poll ()The poll () system call is similar to select () and also polls a certain number of file descriptors to test if they have a ready person.API functions:int poll (struct POLLFD *fds, nfds_t nfds, int timeout);Parameters: nfds+1;struct POLLFD {int FD; /* File Descriptor */Short events; /* Requested Events */Short revents; /* Returned events */}; where the F

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

epoll adoption of event-based readiness notification methods. In Select/poll, the kernel scans all monitored file descriptors only after a certain method is called, and Epoll registers a file descriptor beforehand with Epoll_ctl (), once it is ready based on a file descriptor, The kernel uses a callback mechanism like callback to quickly activate the file descriptor and be notified when the process calls Epoll_wait ().4, Sellect,

downstairs to eat dinner, go to row file called a braised crucian carp. A little extravagant., every day to eat rice bowls a little unbearable, so, a day has passed, the evening should learn!IO multiplexing implemented by the poll function! , together with yesterday's Select function, they are here to achieve the same function, but the poll function is more efficient! A wider range of use!#include #include

the number of file descriptors increases. In addition, the Select () and poll () tell the process that the file descriptor is ready, and if the process does not IO it, the next time you call Select () and poll (), the file descriptors are reported again, so they generally do not lose the ready message. This approach is called a horizontal trigger (level triggered). Third, Epoll It was not until Linux2.6

Turn: Summary of differences between SELECT, poll, Epoll [finishing]The select,poll,epoll is a mechanism for 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,

Summary of differences between SELECT, poll and Epoll [finishing]The select,poll,epoll is a mechanism for 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,epo

recognized as the best performance of the Linux2.6 multi-channel I/O readiness notification method.Epoll can support both horizontal and edge triggering (edge triggered, which only tells the process which file descriptor has just become ready, it only says it again, and if we do not take action then it will not be told again, this way is called edge triggering), The performance of edge triggering is theoretically higher, but the code implementation i

(The following comes from the web and its own summary, thanks again for the insights provided by the great gods on the Web)Before exploring Select poll Epoll We first need to know what is called multiplexing:Come down and explore why multiplexing is used:first, let's look at the complete process of a client request server. First, the request comes in to establish a connection, then receive the data, receive the data, and then send the data.Specific to

The select,poll,epoll is a mechanism for 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 read and write when the read-write event is ready,

select and poll polling, but is implemented by each FD-defined callback function. Only the ready FD will execute the callback function.3. Support for level triggering and edge triggering (just tell the process which file descriptor has just become ready, it only says it again, if we do not take action, then it will not be told again, this way is called edge triggering) two ways, the theoretical edge trigger performance is higher, but the

Description: Linux version 2.6.37.1 Combined with the summary of relevant data and summarized, to make a record, the wrong place please correct, thank you. 1.poll mechanism and wait queue The application layer enters the kernel through the system call poll function, and the kernel executes the corresponding Sys_poll function. Call the Do_sys_poll function in the Sys_poll function. Do_sys_poll function by ca

PHP Instance-AJAX Polls AJAX PollsIn the following example, we will demonstrate a voting program through which the poll results are displayed without refreshing the page.Do you like PHP and AJAX? Example explanation-HTML pageWhen the user selects an option above, a function named "Getvote ()" is executed. This function is triggered by an "onclick" event.The poll.html file code is as follows:HTML

Reprint: http://bookjovi.iteye.com/blog/1186736 Asynchronous IO waiting in Linux is nothing more than three system calls: Select, Poll and Epoll. Many people do not understand the difference between three calls, or the lack of understanding, today on the combination of Linux kernel code detailed description of the three differences. Select The limit to select is the maximum of 1024 fd, you can view the p

About I/O multiplexing:I/O multiplexing (also known as "event-driven"), the first thing to understand is that the operating system provides you with a feature that can give you a notification when one of your sockets is readable or writable. This way, when used with a non-blocking socket, only if the system notifies me which descriptor is readable, I go to the read operation, can guarantee that every read can read the valid data without doing the pure return-1 and eagain of useless. Write operat