polly poll

Reference book: Linux high-performance server programming, is a personal summary of reading, the above consistent Poll system calls are similar to select, (individuals think that poll and select Master one) is also polling a certain number of file descriptors within a specified time to test if there is a ready person. About the prototype of poll #include int

A blocking/nonblocking method is available when an application accesses a device file. If you are using blocking mode, call Open (), read (), write () directly, but the driver layer will determine whether it is readable/writable, and if unreadable/not writable, the current process will hibernate until it wakes up. If you are using non-blocking, you need to use the poll/select mechanism, and the access to the tag file is o_nonblock when you open the fi

returned, including all three sets. If timeout is provided, the returned value may be 0. If an error occurs,-1 is returned, and errno is set to one of the following values:EBADFAn invalid file descriptor is provided to a set.EINTRA signal is captured while waiting, and a call can be initiated again.EINVALThe parameter n is a negative number, or the specified timeout is invalid.ENOMEMInsufficient memory to complete the request.Bytes ---------------------------------------------------------------

All three are UNIX-based multiplexing kernel interfaces. Select is a cross-platform interface, poll is the systemv standard, and epoll is a proprietary Linux interface, which is transformed Based on Poll. Select Function prototype: Int select (int n,Fd_set * readfds,Fd_set * writefds,Fd_set * required TFDs,Struct timeval * timeout );The SELECT statement monitors arrays of multiple file descriptors through s

I believe poll and epoll have been used to read this article. Let's look at the source code of the poll system call. asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout){struct poll_wqueues table;int fdcount, err;unsigned int i;struct poll_list *head;struct poll_list *walk;/* Do a sanity check on nfds ... */if (nfds > current->files->max_fdset nfds > OPEN_MAX) //(1)return

This article mainly introduces Python's method of implementing asynchronous IO through poll, and analyzes the skills related to implementing asynchronous IO through poll, for more information about how to implement asynchronous I/O through poll, see the example in this article. Share it with you for your reference. The specific analysis is as follows:

We're up to the top. With file operations combined with select and poll, blocking operations can be implemented.Select interface:int select (int Nfds, fd_set *readset, Fd_set *writeset,Fd_set *exceptset, struct timeval *timeout);whichNfdsThe number of file descriptors that need to be checked, the value should be the maximum number in the three groups of Fd_setLarger, rather than the total number of actual file descriptors.ReadsetA set of file descript

1. Some disadvantages of selectRecall the Select interfaceint Select (int Nfds, fd_set *readfds, fd_ Set *writefds, fd_set *exceptfds, struct Timeval *timeout);Select requires us to specify the maximum value of the file descriptor, and then take [0,nfds] values in this range to view it in the collection Readfds,writefds or Execptfds, which means there are some file descriptors that are not of interest to us, The CPU did a little work, poll improved

Tags: I/o OS, for SP, file data, on How to manage multiple connections?"What should I do if I want to monitor more than one file descriptor (FD)/connection/stream at the same time ?"Use the select () or Poll () function.Note: Select () is introduced in BSD, and Poll () is the product of sysv stream flow control. Therefore, here we have considerations for porting the platform: Pure BSD systems may still lack

In order to handle a large number of customer connection requests when the Linux socket server is short programming, the use of nonblocking I/O and multiplexing is required, select, poll, and Epoll are the I/O multiplexing provided by the Linux API, and since the addition of Epoll to Linux 2.6, In the field of high-performance server has been widely used, now more famous nginx is the use of epoll to achieve I/O multiplexing support high concurrency, c

The first is to look at common Select and poll. For network programming, it is generally considered that poll is more advanced than Select, which is mainly due to the following reasons: Poll () does not require the developer to calculate the maximum file description Fugai size. Poll () is faster when deali

Python uses poll to Implement Asynchronous IO This example describes how Python implements asynchronous IO through poll. Share it with you for your reference. The specific analysis is as follows: Poll object is returned after poll () is used. This object supports the following methods: PollObj. register (fd, [, eventma

Python implements asynchronous IO through poll, and pythonpoll asynchronous io This example describes how Python implements asynchronous IO through poll. Share it with you for your reference. The specific analysis is as follows: Poll object is returned after poll () is used. This object supports the following methods:P

1, what is the poll method, what is the function?2. Select System Call (function)Select system calls are used for multi-channel monitoring, and select blocks the calling process when no file satisfies the requirement.int select (int maxfd, fd_set *readfds, Fd_set *writefds, fe_set *exceptfds, const struct Timeval *timeout)Select System Invocation (Parameters)1) Maxfd:The range of file descriptors is 1 larger than the maximum file descriptor to be dete

For the poll model listener events and return events, we define the following macros: #define kreadevent (Pollin | POLLPRI)#define kwriteevent (pollout | Pollwrband)#define kreadrevent (Pollin | Pollpri | Pollrdhup)#define kwriterevent (pollout)We explained earlier why the non-blocking IO must have buffers. In fact, for server, each TCP connection should have two buffers, one for input and one for output. sockfd–> inputbuffer–> User space –>

In the previous sections we discussed the basic concepts of nonblocking IO, the design of buffer and the implementation of non-blocking connect, which we now use to complete the client's writing. As we have suggested in http://www.cnblogs.com/inevermore/p/4049165.html, the client needs to monitor stdin, stdout, and SOCKFD. It's important to note that Only the buffer can be written, only to listen to SOCKFD and stdin read events. In the past in blocking IO, we always listen to SOCKF

If an application handles multiple devices, such as applications that read network data, keys, and serial ports, there are three ways to think about it:Method 1:Serial + blocked mode reads:while (1) {Read (standard input);Read (network);}Disadvantage: Whenever blocking reads the standard input, if the user does not perform the standard input operation, and the client sends the data to the server, the server cannot read the data sent by the client!Method 2:Use multi-threaded or multi-process mech

operation and does not need to wait, but immediately gets a result. When the user process determines that the result is an error, it knows that the data is not ready, so it can send the read operation again. Once the data in the kernel is ready and again receives the system call of the user process, it immediately copies the data to the user's memory and then returns. Therefore, nonblocking IO is characterized by the user process needs to constantly proactively ask kernel data well no. I/O mult

Introduction to select, poll, EpollEpoll and select provide a multi-channel I/O multiplexing solution. In the current Linux kernel can be supported, where Epoll is unique to Linux, and select should be POSIX rules, the general operating system has implementedSelectSelect essentially processes the next step by setting or checking the data structure that holds the FD flag bit. The disadvantages of this are:1, a single process can monitor the number of F

Linux network protocol stack is very independent, up and down through two interfaces, respectively, and the user state and device connected, can also be considered as the North and South interface ... North through the socket interface, south through the Qdisc interface (you can think of the upper Netdev queue, for the receiving interface, NAPI poll queue is another example), whether the socket or QDISC, is based on the queue to manage, that is, Three