time wait linux

Linux Process understanding and practice (4) wait function processing botnetsWait background When a child process exits, the kernel sends a SIGCHLD signal to the parent process. The exit of the child process is an asynchronous event (the child process can be terminated at any time when the parent process is running) When a child process exits, the kernel changes

the background of waitWhen the child process exits, the kernel sends a SIGCHLD signal to the parent process, and the exit of the child process is an asynchronous event (the child process can terminate at any time the parent process runs)When a child process exits, the kernel resets the subprocess to zombie state, a process called a zombie process that retains only the smallest number of kernel data structures so that the parent process queries the exi

have stopped is provided even if this option is not specified. WCONTINUED (since Linux 2.6.10) also return if a stopped child has been resumed by delivery of SIGCONT. Wait until it is not terminated. Now let's look at the difference between wait () and waitpid () through the instance. By modifying the client program, you can c

amount of memory used as a buffer. Cache: Used as the memory size for caching, if the cache value is large, it indicates that there are many files in the cache, and if the frequently accessed files can be cached, the disk's read IO bi will be very small. Swap? Si: Writes from the swap area to the memory size per second, and the disk is transferred into memory. So: The amount of memory written to the swap area per second is transferred from memory to disk. Note: When memory is sufficient, these

statement in the parent process: signal (SIGCHLD, SIG_IGN); indicates that the parent process ignores the SIGCHLD signal, this signal is sent to the parent process when the child process exits. 3. SIGCHLD Signal When a child process exits, the kernel sends a SIGCHLD signal to the parent process. The exit of the child process is an asynchronous event (the child process can be terminated at any time when the parent process is running) If you do not w

 Linux kernel wait queue inquiry-wait_queue_t-wait_queue_head_t 【 Related source version: Linux kernel source version: linux-3.0.86 Uboot version: uboot-2010.12. Android System Source version: Android-5.0.2 " Waiting queues are one way in which the Linux kernel implement

1.pid_t Fork ();(1) When a process calls fork, a child process is created. This subprocess differs from the parent process only by his process ID and the parent process ID, and the rest are the same. Just like the character process clone (clone) itself.(2) to differentiate between parent and child processes, we must track the return value of fork. The fork return value plays an important role when the fork fails (not enough memory or the user's maximum number of processes has arrived) Fork retur

If a child process is preceded by a parent process, the wait () function is invoked by the parent process and the wait () function is not invoked to produce two different results:--> If the parent process does not invoke the wait () and the Waitpid () function, the child process enters a zombie state.--> If the parent process calls the

I/O wait for Linux system monitoring and diagnosis tools Directory 1. Problem:2. troubleshooting:2.1 vmstat2.2 iostat2.3 iotop3. The last words: a different path1. Problem: Recently, log real-time synchronization was performed. Before the release, the online log stress test was performed. The message queue and the client and the local machine are normal, but I di

), you can see the CPU in the IO waiting value will be greater.System (Systems)? In: Number of interrupts per second, including clock interrupts.? CS: The number of context switches per second.Note: The larger the 2 values above, the greater the CPU time that is consumed by the kernel.CPU (expressed as a percentage)? US: Percentage of user Process Execution timeWhen the value of us is higher, it means that the user process consumes more CPU

Original URL: http://blog.163.com/libo_5/blog/static/15696852010324287748/ Zombie does not consume memory or CPU, and on the surface we can not care about their existence, but in fact the UNIX system limits the maximum number of processes that can exist at a time. If the program does not clean up the zombie in the system in time, it will eventually result in too many processes, and when a new p

Wait Queue: In Linux driver programming, waiting queues can be used to implement blocking of processes. The wait queue can be thought of as a container for the save process, and the process is placed in a wait queue when the process is blocked; When the process is awakened, the process is fetched from the

1. Linux wait 1) function: wait until the sub-process is interrupted or terminated2) header files# Include # Include 3) Function Definition: pid_t wait (int * status );4) Function DescriptionWait () temporarily stops the execution of the current process until a signal arrives or the child process ends. If the child pro

executed) If you change to 0 and then add pthread_exit (NULL) after sleep (2), the result is: à with pthread_cleanup_pop (1); The result is the same. Example: Use Pthread_cleanup_push and Pthread_cleanup_pop to release memory space allocated by child threads #include #include #include void Freemem (void * args) { Free (args); printf ("Clean up the memory!\n"); } void* threadfunc (void *args) { Char *p = (char*) malloc (10); Allocate Memory for yourself Pthread_cleanup_push (FREEMEM,P); int i

I. botnets When a child process exits, the kernel sends a sigchld signal to the parent process. The exit of the child process is an asynchronous event (the child process can be terminated at any time when the parent process is running)When a child process exits, the kernel changes the child process to a zombie state. This process is called a zombie process. It only retains the smallest kernel data structure, so that the parent process can query the ex

Waitqueue (name, tsk) 7 wait_queue_t name = __waitqueue_initializer (name, tsk)The task_list waiting queue joins the task_list linked list waiting for the queue header. The wait_queue_func_t is typically assigned the following default handler:1 int int Sync, 2 void *key)3{4 return try_to_wake_up (curr-> Private , mode, sync); 5 }1.3 Add/Remove wait queues1 StaticInlinevoid__add_wait_queue (wait_queue_head_t *h

In the morning a RABBITMQ and Java server, the client feedback Super card, see IO and CPU is not high. After finding sixty thousand or seventy thousand messages squeezed, the temporary problem solved, looking at/var/log/messages, found many tcp:time wait bucket table overflow, as follows:Nov 10:36:08 iz237hn51s7z kernel:TCP:time wait bucket table overflowNov 10:36:08 iz237hn51s7z kernel:TCP:time

(). The following comes from: http://tauruspdj.blog.163.com/blog/static/4312500620090794030998/ The simplest form of hibernation in Linux is the following macro,Wait_event (queue, condition)/* process will be placed in non-interrupted hibernation (uninterruptible sleep) * *Wait_event_interruptible (queue, condition)/* process can be interrupted by a signal sleep, return a value of not 0 to indicate that the sleep is interrupted by a signal * *Wait_e

This article has been transferred from Reille blog: http://velep.com/archives/815.html Waiting queues play a pivotal role in the Linux kernel, and many Linux drivers are more or less involved in waiting queues. Therefore, for the Linux kernel and driver developers, mastering the waiting queue is one of the necessary lessons. The waiting queue of

First, zombie process When the child process exits, the kernel sends a SIGCHLD signal to the parent process, and the child process exits as an asynchronous event (the child process terminates at any time the parent process runs) When a child process exits, the kernel leaves the subprocess as a zombie, a process called a zombie process that retains only the smallest kernel data structure so that the parent process queries the exit state of the child