mmap mindmap

Forwarded by: Http://blog.chinaunix.net/uid-26669729-id-3077015.htmlMmap detailed description of Linux memory managementOne. 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 out. Munmap performs the opposite operat

At the operating system level, the virtual address space seen by each process is independent and there is no intersection between them. Therefore, you need to map different virtual addresses of multiple associated processes to the same physical address space through an intermediate Association. MMAP is such a function. it treats a file (also... information nbs) as the virtual address space seen by each process is independent at the operating system l

The memory between the different processes is independent of each other, there is no way to directly manipulate each other's data, while the shared memory is provided by the operating system memory mapping mechanism, so that the different processes of a single address space mapped to the same virtual memory area, so that different processes can operate to a common block of memory. Shared memory is the most efficient inter-process communication mechanism because the data does not need to be repli

First, IntroductionLinux provides a memory-mapped function mmap, which maps the contents of a file to a piece of memory (accurate virtual memory), through the memory read and modify, to realize the file read and modify, first look at the MMAP function declaration: Header file: Prototype: void *mmap (void *addr, size_t length,

background Recently in the analysis of problems, encountered MMAP FB equipment failure problem, by the way to see the next 4.1 version of the kernel of the mmap related process, previously seen the old version, some forget, here right when records for follow-up reference. what Mmap is. Believe that a brother who has done Linux development more or less used, or

Environment: Ubuntu9.04 the precautions for using mmap () in 2.6.28.10 kernel (as shown in kernel 2.6.25 +) are not mentioned here. In the new kernel, there are two options related to mmap () ing memory/dev/mem: CONFIG_X86_PAT and CONFIG_STRICT_DEVMEM. The kernel contains the following: CONFIG_STRICT_DEVMEM: Ifthisopti Environment: Ubuntu 9.04 Let's talk about the precautions for using

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 mmap the file to/tmp.For m

Function Prototypes:void *mmap (void *addr, size_t length, int prot, int flags, int fd, off_t offset);Function: Maps a file to a process memory space with addr as the starting address, and when called, typically passes the addr parameter to NULL, and the kernel chooses the starting virtual address spaceThe corresponding Munmap (2) system call is de-mapped, and the in-memory data is written to the file. As you can see, after calling Munmap, the pointer

(the data structure is used here because the data in the shared memory area is usually in a fixed format, which is determined by the communication processes, the structure is generally representative ). Map_normfile1 first open or create a file, and set the file length to 5 people structure sizes. Then, 10 people structures are set starting from the return address of MMAP. Then, the process sleep for 10 seconds, wait for other processes to map the sa

Comparison between MMAP and read/write on File Access We know that files accessed through MMAP or read/write must be cached in the kernel. When you need to read and write content from the file, the files are copied to the cache in the kernel for communication. 1. in read/write mode, the user must specify the number of reads to the kernel, and then copy the obtained content from the kernel cache to the use

At the operating system level, the virtual address space seen by each process is independent and there is no intersection between them. Therefore, you need to map different virtual addresses of multiple associated processes to the same physical address space through an intermediate Association.MMAP is a function that maps a file (that is, the physical address space in the memory) to the address space of different processes.I. WriteIt is worth noting that MMA