mmap mindmap

operation of the first process ends. The programmer is responsible for the synchronization of shared memory access. Optional Synchronization Methods include mutex lock, condition variable, read/write lock, record lock, and traffic signal. Related functions 1 MMAP () function 2 Function: maps a file or POSIX shared memory area object to the address space of the calling process. 3 Header file: # include 4 Function prototype:Void *

device. The primary device number is 29, and the secondary device number ranges from 0 to 31. Corresponding to/dev/fb0-/dev/fb31 respectively. Through/dev/FB, application operations mainly include: 1. read/write/dev/FB: equivalent to the read/write screen buffer. For example, you can use the CP/dev/fb0 TMP command to copy the content of the current screen to a file, the command cp tmp>/dev/fb0 directly displays the image file TMP on the screen. 2. Map operation: since Linux is working in protec

This is a creation in Article, where the information may have evolved or changed. Plug-in storage engine API MONGODB3.0 introduced the plug-in storage Engine API, which makes it easy for third-party storage engine vendors to join MongoDB, a change that undoubtedly references MySQL's design philosophy. At present, in addition to the early Mmap storage engine, Wiredtiger and ROCKSDB have completed the support for MongoDB, the former is the acquisition o

an issue caused by a process memory layout exceptionThe previous period of time the business reflects a certain type of server update bash, SSH connected to the occasional login failed, the client spit error message as follows:Figure-0This version of Bash is customized for the Department, but the implementation has not changed the original logic, but added some monitoring functions, then where do these errors come from?Is it bash's pot?From the above error message can be guessed that the excepti

-dimensional, when the programmer identifies an address, it needs to give both the segment name and the address in the paragraph. (3) Under what circumstances does malloc invoke mmap?From the operating system perspective, the process allocates memory in two ways, with two system invocations: BRK and mmap (regardless of shared memory). BRK is to push the highest address pointer of the data segment (. da

top chunk size to MinSize + NB, reset the memory size used by the allocation area and set top Chunk size to new value (note that the size here cannot be set directly to MinSize + NB because there is an alignment operation in Grow_heap). Assuming that grow_heap fails, most of the time that the use of heap is close to its maximum heap_max_size, only one heap can be reassigned through NEW_HEAP, and the incoming parameter mp_.top_pad indicates that when memory is allocated, Extra memory allocated

This article from: HTTP://WWW.OPEN-OPEN.COM/LIB/VIEW/OPEN1427078982824.HTML#_LABEL3For more information, see official website: http://docs.mongodb.org/manual/release-notes/3.0/Reference article:Test: http://www.mongoing.com/archives/862Http://www.mongoing.com/benchmark_3_0Configuration: Http://www.mongoing.com/config_3_0Learning: http://www.mongoing.com/Migration: Https://github.com/xbsura/mongo-migrateThe introduction was officially released on March 3, 2015 after the revision of the version nu

(physical page,pp), and the size is also p-bytes (physical pages are also called page frames).At any one time, the collection of virtual pages is divided into three disjoint subsets: Unassigned : A page that the VM system has not yet assigned (or created). Unallocated blocks do not have any data associated with them, so they do not occupy any disk space. (No calls to malloc or mmap) Cached : The allocated pages in the physical store are

corresponding physical page, and releasing it all out of the process .char *p=malloc(2048) //这里只是分配了虚拟内存2048，并不占用实际内存。strcpy(p,”123”) //分配了物理页面，虽然只是使用了3个字节，但内存还是为它分配了2048字节的物理内存。free(p) //通过虚拟地址，找到其所对应的物理页面，释放物理页面，释放线性区。We know that the user's process and kernel are running at different levels, and the communication between the process and the kernel is done through system calls. Processes in the application and release of memory, mainly through the brk,sbrk,

instead use a relative address:mov[qword addr],rax ;okmov[rel addr],rax ;oktooHowever, there is no such restriction under linux64.6 MAC64 and linux64 are different from the C library wrapper of the system call, especially when the return value of the system call is processed, such as Mmap call, linux64 C library does not seem to check the parameters, but the syscall itself checks, and MAC64 checks the parameters before the call, if the parame

. Example #include Main (){printf ("Page size =%d\n", getpagesize ());} malloc (Configure memory space) Related functions Calloc,free,realloc,brk Table header File #include Defining functions void * malloc (size_t size); Function description malloc () is used to configure the memory space, which is determined by the specified size. return value Ret

What's an APC?Alternative PHP cache (APC) is a valid open source Cache tool for PHP, and he is able to cache opcode PHP intermediate code.PHP APC provides two kinds of caching functions, namely cache opcode (target file), we call it apc_compiler_cache. It also provides interfaces for PHP developers to host user data in memory, which we call Apc_user_cache. We are here mainly to control the configuration of PHP-APC.Installing the PHP APCAs a test environment, we use CentOS5.3 (2.6.18-128.EL5PAE)

type needs to be shown, as shown in Figure 2. Figure 2 The difference between mutable and immutable can be preliminarily understood by naming, the former can modify the content, and the latter cannot be modified after initialization. As shown in Figure 3, adding elements to the map and mmap in Figure 2, the map failed while trying the + = operation, and mmap successfully modified the content, adding "(" C

Function: Mmap ()Function: Creates a memory map area, maps the file data on disk to memory, and the user can modify the disk file through memory.Advantages: High EfficiencyCons: Do not block, trouble (for efficiency is not very high demand advice with piping)Function Prototypes:#include void *mmap (voidint int int FD, off_t offset); int munmap (void *addr, size_t length);

phpinfo. B. install APC in LIUNXStep 1: Download and InstallWget http://pecl.php.net/get/APC-3.1.8.tgzTar-zxvf APC-3.1.8.tgz cd APC-3.1.8/Usr/local/php/bin/phpize. /Configure -- enable-apc -- enable-mmap -- enable-apc-spinlocks -- disable-apc-pthreadmutex -- with-php-config =/usr/local/php/bin/php- configMakeSudo make installStep 2: Configure APCAdd the following configuration items to/usr/local/php/etc/php. ini: The code is as follows:Extension = "a

state. The third step, the write() context switch, copies the buffer to the kernel address buffer. Fourth step, write() return, fourth context switch, DMA engine transmits the data from the kernel buffer to the protocol engine, usually enters the queue, waits for the transmission. We see that the data is copied back and forth between the user space and the kernel space, which is not necessary. The solution is: mmap , sendfile , specifically

V4L2 driver (1). Overall framework, v4l2driver 1.1 starting from character Devices Anyone familiar with v4l2 user space programming knows that v4l2 programming mainly calls a series of ioctl functions to open, close, query, and set v4l2 devices. the v4l2 device is a character device, and the main task of its driver is to implement a variety of ioctl .?Shows the overall framework of v4l2. What is the overall framework of V4L2? The light green background is the user space, and the light bl

://pecl.php.net/get/APC-3.1.8.tgzTAR-ZXVF apc-3.1.8.tgz CD APC-3.1.8/usr/local/php/bin/phpize./configure--ENABLE-APC--enable-mmap--enable-apc-spinlocks--disable-apc-pthreadmutex--with-php-config=/usr/ Local/php/bin/php-configMakesudo make installStep Two: Configure APCAdd the following configuration entries in/usr/local/php/etc/php.ini:Copy CodeThe code is as follows:Extension = "apc.so";; APC settingapc.enabled = 1Apc.shm_segments = 1Apc.shm_size = 6

://pecl.php.net/get/APC-3.1.8.tgzTAR-ZXVF apc-3.1.8.tgz CD APC-3.1.8/usr/local/php/bin/phpize./configure--ENABLE-APC--enable-mmap--enable-apc-spinlocks--disable-apc-pthreadmutex--with-php-config=/usr/ Local/php/bin/php-configMakesudo make installStep Two: Configure APCAdd the following configuration entries in/usr/local/php/etc/php.ini:Copy CodeThe code is as follows:Extension = "apc.so";; APC settingapc.enabled = 1Apc.shm_segments = 1Apc.shm_size = 6

receiver does not know how much cache is required, you can only open up as much space as possible or call the API to receive the message header to obtain the message body size, and then open up an appropriate space to receive the message body. Both methods are insufficient, either a waste of space or time. The binder adopts a new policy: the binder driver is responsible for managing the data receiving cache. We have noticed that the binder driver implements