mmap mindmap

The/dev/mem driver provided in the Linux kernel provides a channel for us to read and write memory physical addresses. Here are 2 ways to read and write physical addresses using MEM device files, one for device-driven and the other for system calls. First we look at the mem this device file,/dev/mem is a character device under Linux, the source file is ~/DRIVERS/CHAR/MEM.C, this device file is specifically used to read and write physical address. The contents are the address of all physical memo

generated data. 4. stack for saving local variables and implementing function calls. 5. The mmap method is used to map the memory segments in the virtual address space. Therefore, you only need to view the user-State virtual address space allocation of any thread to know the total memory occupied by all threads in the same process.. You can view the/proc/{pid}/maps file to obtain the relevant virtual address space content. some typical contents in th

brightness, hue, contrast, whiteness, and depth;* Video_mmap is used for memory ing;* The frame information mapped by voido_mbuf using MMAP is actually the frame information entered into the camera memory buffer, including size (frame size) and frames (maximum number of frames supported) and offsets (the offset of each frame to the base address ).Main System Call functions used in the program include: open ("/dev/voideo0", int flags), close (FD),

Ramcloud source code analysis (III)　　1. Overview　　This section mainly analyzes the servers in the ramcloud system. This section focuses on memory management and corresponds to the log-structured memory for dram-based storage article on fast '14. First, log-based memory management is copying allocators. The main purpose is to meet the following requirements: first, fragments can be eliminated through copy object; second, garbage collection can be implemented without global scanning. The first req

address to a physical address );5. Re-execute the command with a page disconnection;If you need to read the disk in step 1, the page Disconnection will be majflt; otherwise, it will be minflt.The minflt of this process is so high that it can be used more than 10000 times a second, so it has to be suspected that it has a lot to do with the consumption of the kernel-mode CPU of the process. Analyze codeCheck the code and find that: a request uses malloc to allocate 2 MB of memory and free the mem

by Shm_open (), which returns a pointer to memory. (In some cases, you can also map the file descriptor of a generic file or another device to memory.) The implementation of Mmap is also based on the above principle, when using Mmap to map a file (or part of a file) to the address space of the process, and does not load the file data, but only in the process of the virtual address space to divide a block,

i_writecount-related scenario for writing files: When you write to open a file, in the function Dentry_open: Copy Code code as follows: if (F->f_mode Fmode_write) { Error = get_write_access (inode); if (Error) Goto Cleanup_file; } Of course, when the file closes, the i_writecount--is executed, and the code executes when it closes: Copy Code code as follows: if (File->f_mode Fmode_write) Put_write_access (Inode); The Put_write_access code

segment. The top 128TB is used by the kernel and cannot be accessed directly by the application. The stack of applications begins to grow downward from a high address. The space between the BSS segment and the stack is free, the free space is divided into two parts, one is heap, and the other is the mmap mapping area. The mmap region grows relative to the stack area. On different Linux kernels and machines

In linux, the Mind Map software kdissert-general Linux technology-Linux technology and application information. The following is a detailed description. Author: Ji Qing email: jiqingwu@gmail.com Mainpage: http://hi.baidu.com/jiqing0925 I like thinking with mind maps, and I like freemind very much in windows. After switching to linux, you can continue to use freemind. However, I found another brain Graph Software, kdissert, is in the source. It feels good to use it. Although it is not a

has an animated effect when displaying or hiding the terminal window. I think this will make people feel smoother and more natural, instead of suddenly popping up to scare people. * The tag function is available. This eliminates the need to start multiple terminal instance programs at the same time. If it is not enough, open the tag again. However, I prefer to work with screen now. * Customization. You can customize the window size and position to meet your individual needs. Ii. freemind Projec

Freemind: Recommended items for SourceForge this month Author: chelong published on: Last updated on:Copyright statement: You can reprint it as needed. During reprinting, you must mark the original source and author information of the article and this statement in the form of a hyperlink.Http://www.chedong.com/blog/archives/001121.html This month: 2006-02 recommended SourceForge project: freemind Mindmap: Mind Map. This is a way of organizing ideas l

technical points not only improves my personal abilities, but also helps the software re-architecture to a great extent. Thanks to the conversion of the platform, we have the opportunity to re-analyze and design the original system. I used to be a complete implementer, but now I am playing more of a designer. This shift in roles means greater responsibility. If something goes wrong, it is not a waste of time but a waste of team resources as a whole. When I wrote a summary last year, I was looki

attaching new files should is specified. Zotero LibreOffice integration:bibliography Management Mindmap Freeplane:for dumping ideas from the brain and organizing information and knowledge with complicated structures and inter Connections. Docear + jabref:for Organizing bibiliography information using a MINDMAP methodology. Term

* malloc (size_t size ); Function Description Malloc () is used to configure the memory space, which is determined by the specified size. Return Value If the configuration is successful, a pointer is returned. If the configuration fails, null is returned. Example Void P = malloc (1024);/* configure 1 kb of memory */ 　 MMAP (Create memory ing) Related functions Munmap, open

Inter-process communication in Linux (5): Shared Memory (2) The system calls MMAP () to map a common file to implement shared memory. System V maps files in the SHM of a special file system to implement shared memory communication between processes. That is to say, each shared memory area corresponds to a file in the shm of the special File System (this is linked through the shmid_kernel structure), and will be elaborated later. 1. Principle of System

* malloc (size_t size ); Function Description Malloc () is used to configure the memory space, which is determined by the specified size. Return Value If the configuration is successful, a pointer is returned. If the configuration fails, null is returned. Example Void P = malloc (1024);/* configure 1 kb of memory */ MMAP (Create memory ing) Related functions Munmap, open

/Dev/MEM: full image of physical memory. It can be used to access the physical memory. /Dev/kmem: The full image of the virtual memory seen by the kernel. Can be used to access the contents of the kernel. /Dev/MEM is used to access physical Io devices, for example, X is used to access the physical memory of the graphics card or access gpio in embedded systems. Use The method is generally open and then MMAP can use the address after map to access the p

The/dev/MEM driver provided in the Linux Kernel provides a channel for us to read and write the physical address of the memory. The following describes two methods to read and write physical addresses Using Mem Device Files: one is a device driver and the other is a system call. First, let's take a look at the mem device file./dev/MEM is a character device in Linux. The source file is ~ /Drivers/Char/MEM. C. This device file is used to read and write physical addresses. The content is the addres

Reprinted from http://www.ibm.com/developerworks/cn/linux/l-ipc/part5/index2.html The system calls MMAP () to map a common file to implement shared memory. System V maps files in the SHM of a special file system to implement shared memory communication between processes. That is to say, each shared memory area corresponds to a file in the shm of the special File System (this is linked through the shmid_kernel structure), and will be elaborated later.

Directory 1. Write in front 2.devmem use 3. Application Layer 4. Kernel Layer 1. Write in frontRecently, when debugging, you need to access physical memory at the user level, and the application layer can use the devmem tool to access the physical address. View the source code, is actually the /dev/mem operation, through the mmap can map the physical address to the virtual address of the user space, completes the reading and