mmap

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, which is especially beneficial for large files or frequently accessed files. But one thing

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 file is mapped to the memory. Therefore, communication be

between processes, the mappings are not always read and written, and when there is new communication, 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

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

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 multiple pages, and if the size of the file is not

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 out. Munmap performs the opposite operation by deleting the object mappings for a specific

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 of virtual storage.,On the one hand, file ing provides users with a set of measures, as if users map files to a part of their own addre

Memory Allocation in linux: mmap, munmp, brk, mmapbrk Linux virtual memory management has several key concepts: 1. Each process has an independent virtual address space. The virtual address accessed by the process is not a real physical address; 2. The virtual address can be mapped to the physical address through the page table on each process (in the kernel virtual address space of each process) to obtain the real physical address; 3. If the physica

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 process can read and write the memory in a pointer way, and the system will automatically write back the dirty page to the corresponding file

Memory mapping is one of the most interesting features of modern Unix systems. As for drivers, memory mappings can be implemented to provide direct access to device memory by user programs. A clear example of a mmap usage can be seen from a subset of the virtual memory areas that are viewed to the X Windows system server: Cat/proc/731/maps 000a0000-000c0000 rwxs 000a0000 03:01 282652/dev/mem 000f0000-00100000 r-xs 000f0000 03:01 282652/dev/mem 004000

In Linux, MMAP and mmap2 are called to create a process address space ing. MMAP and mmap2 are commonly used in the following scenarios: 1. file ing common file I/O operations, read and write the memory after MMAP ing, you can complete file read and write operations, kernel and userspace operations are the same physical memory; while regular file read and write op

Http://blog.csdn.net/edwardlulinux/article/details/8604400 Many articles have analyzed the implementation principle of MMAP. From the logic of the code, I always feel that the read/write ing area after MMAP is not associated with the common read/write areas. Have to have questions: 1. What is the difference between reading and writing in the ing areas after the common read/write and

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

One. 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 operation by deleting the object mappings for a specific address area.When using the mma