mmap file

Original: http://weibo.com/p/1001603830912709174661Write mmap memory and file generates hundreds of MS latency reasonApril 12, 2015 21:10 reading 4274 Recently saw a bug introduction, the author spent 4 months tracking location, found that the JVM statistics will cause the garbage collection process to pause good hundreds of Ms. The JVM statistics are written to a memory area that

Disk-to-memory mapping is a file mapping, before we say the swap, because This problem makes me very easy to think of Swap,linux swap is the meaning of the swap partition, in the case of memory not enough, the operating system first put the memory and the swap area of the disk to "map", and then the these memory freed up into memory, For the subsequent process of freeing up a piece of memory space, wait until the own process is awakened again, then

/ * Use Mmap to operate the file * /#include #include #include #include #include #include #define FILELENGTHintMainvoid){intFD =-1;/ * The string that will be written to the file * / Charbuf[]="Quick brown fox jumps over the lazy dog";Char*ptr = NULL;/* Open the file mmap.txt and reduce the

void *mmap (void *addr, size_t length, int prot, int flags, int fd, off_t offset);function function: Map the contents of the file to a piece of memory (virtual memory), through the memory read and modify, to achieve the file read and modify.Parameter descriptionAddr: Specifies the starting address of the map, usually set to null (indicated by the system).Length:

Article Title: Linux mmap File Memory ing mechanism. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source. When describing the concept of file ing, it is inevitable that virtual memory (SVR 4 VM) is involved ). in fact,

This article describes the POSIX environment uses file mapping IO method of operation, file mapping IO also known as storage mapping IO , for ordinary files, many times it is efficient, it actually reduces the duplication of data, and it can also be used in special places for communication between processes, a way of sharing memory. We can think of a file as a co

MMAP can map a part of the disk file directly to the memory, so that the location in the file has a corresponding memory address, you can directly use pointers to read and write files without the need for the read/write function. Prototype: # include Void * MMAP (void * ADDR, size_t Len, int Prot, int flag, int fi

Best references: 1. Master from the Internet. 2. UNP V2 posix ipc chapter 12. 3. Linux man command. Article 1: MMAP function Purpose 1. Map common files to the process memory space for memory ing Io. 2. Map special files to the process memory space for anonymous memory ing Io. 3. Map shm_open to open the POSIX shared memory zone to the memory space of the process, which can provide data sharing and IO among unrelated processes. # Include V

Note: This example uses the form of shared file ing. The write end writes data and the read end reads data. Write end: /*-------------map_normalfile1.c-----------*/#include Read end: /*-------------map_normalfile2.c-----------*/#include

Turn from: http://www.perfgeeks.com/?p=723 Mmap () and MMAP2 () are often visible through strace statistical system calls. System call MMAP () can map a file to memory (process space). This allows the operation of the file to be converted to memory operations to avoid more lseek () and read (), write () operations, w

Linux system programming: inter-process communication-mmap, linux-mmap Inter-process communication-mmap #include In essence, mmap synchronizes the memory with files on the hard disk. The content in a memory is synchronized to the hard disk file, that is, the

shared memory area is again established. Instead, keep the shared area until the communication is complete so that the data content is kept in shared memory and not written back to the file. Content in shared memory is often written back to the file when the mapping is released. Therefore, the use of shared memory communication mode is very high efficiency. The Linux 2.2.x kernel supports a variety of shar

Shared Memory-memory ing MMAP Shared memory is the most useful method for inter-process communication and the fastest IPC format. The shared memory of two different processes A and B means that the same physical memory is mapped to the process address spaces of process a and process B. Process A can immediately see the updates to data in the shared memory of process B, and vice versa. Because multiple processes share the same memory area, a synchron

SELF: http://hi.baidu.com/flying5/blog good blog, you can go to have a look Linux MMAP File Memory ing mechanism MMAP: Memory Map When talking about the concept of file ing, it is inevitable that virtual memory (SVR 4 VM) is involved. In fact,File ing is the central concept

Mmap Basic ConceptsMmap is a memory-mapped file method that maps a file or other object to the address space of a process, implementing a one by one-mapping relationship between the file disk address and a virtual address in the process virtual address space. After such a mapping relationship is implemented, the proces

The previous article learned about shared memory: http://www.cnblogs.com/charlesblc/p/6142139.htmlAccording to this http://blog.chinaunix.net/uid-26335251-id-3493125.htmlOne more article:1. Shared memory allows two or more processes to share a given store, because the data does not need to replicate back and forth, so it is the fastest inter-process communication mechanism. Shared memory can be implemented through the mmap () mapping of ordinary files

Note: The android underlying malloc is swapped for mmap to get memory, the acquired memory can be added to the tag, so that the meminfo for analysis, you can view the memory of the tag separately for analysis.One. Mmap system call1. Mmap system callMmap maps a file or other object into memory. Files are mapped to multi

Reprinted from Http://blog.chinaunix.net/uid-26669729-id-3077015.htmlOne. Mmap system call1. Mmap system callMmap maps a file or other object into memory. Files are mapped to multiple pages, and if the size of the file is not the sum of the size of all pages, the space that is not used by the last page will be zeroed o

. (including: code segment and rodata segment (C constant string and # constant defined by define )) 2. Data Segment: space for saving global and static variables; 3. Heap: the dynamic memory that we usually call. Most of malloc/new comes from this. The heap top position can be dynamically adjusted using the brk and sbrk functions. 4. File ing area: memory mapped to physical space, such as dynamic library and shared memory, is generally the virtual ad

server, which transmits large amounts of data to and from video memory; Dynamic mapping graphics display to user space improves throughput as opposed to a lseek/write implementation. Another typical example is a program that controls a PCI device. Most PCI peripherals map their control registers to a memory address, and a high-performance application might prefer direct access to registers instead of repeatedly calling IOCTL to complete its work. The Mmap