mmap file

Solemnly declare: This article is written by the author based on my personal understanding. errors are inevitable. Please be prepared! You can reprint, modify, and indicate the source when reprinting! When you run sudo apt-Get update, the system prompts: E: Dynamic MMAP has no space. Increase the size of APT: cache-limit. Current Value: 25165824. (MAN 5 apt. conf), E: Error Handling libsvg-ruby1.8 (newfilever1), E: Problem with mergelist/var/lib/AP

1. Write filesWith open ('?? ' ' r+b ' As F: With contextlib.closing (Mmap.mmap (F.fileno (), size, flags=mmap. map_shared, access=mmap. Access_write)) as mm: = ?? Mm.flush ()2. Key Reminders>>> mmap.ACCESS_READ1>>> mmap.ACCESS_WRITE2>>> mmap.ACCESS_COPY3>>> mmap.ACCESS_READ | mmap.ACCESS_WRITE3In and words, is the access=mmap.ACCESS_READ|mmap.ACCESS_WRITE same as access=mmap.ACCESS_COPY . What do

http://lwn.net/Articles/28746/ Occasionally, a device driver would need to map an address range into a userprocess ' s space. This mapping can is done into give the process DirectAccess to a device ' I/O memory area, or to the driver ' s DMA buffers. 2.6features a number of changes to the virtual memory subsystem, but, for Mostdrivers, supporing mmap () would be relatively Painless. Using Remap_page_range () There are two techniques in with for imple

("/dev/mem", O_RDWR | O_sync)) = =-1) { printf ("/dev/mem could not being opened.\n"); Perror ("open"); Exit (1); } Else { printf ("/dev/mem opened.\n"); } / * MAP one page * / Map_base = mmap (0, map_size, Prot_read | Prot_write, map_shared, FD, Target ~map_mask); if (map_base = = (void *)-1) { printf ("Memory map failed.\n"); Perror ("mmap"); } Else { printf ("Memory

When writing a device driver, if you want to map the device memory to the user space, you need to implement MMAP. by reading the ldd3 introduction above, you have a little understanding of MMAP implementation. This article describes how to use Int remap_pfn_range (struct vm_area_struct * VMA, unsigned long effec_addr, Unsigned long PFN, unsigned long size, pgprot_t prot) function or Int io_remap_page_range

1. An error is reported when ORACLE software is installed to 86%. The figure is missing. The log is as follows: /Oracle/u01/app/oracle/product/11.2.0/INFO: db_1/lib/sysliblist '-R/opt/SUNWcluster/lib-R/export/home/oracle/u01/app/oracle/product/11.2.0/db_1/lib-R/opt /ORCLcluster/lib/-y p, :/opt/SUNWcluster/lib:/opt/ORCLcluster/lib/:/usr/ccs/lib/amd64: /usr/lib/amd64-Qy-lm/export/home/oracle/u01/app/oracle/product/11.2.0/db_1/lib/prod/lib/amd64/crtn. o-lpthread INFO: ld: fatal:

The video application can apply for a buffer from the v4l2 driver in two ways. 1. userptr, as the name implies, refers to the user space pointer. the application layer allocates the required memory space and passes it to the v4l2 driver layer as a pointer, the v4l2 driver saves the content of capture to the space indicated by the pointer. In general, the application layer needs to ensure that the memory space is physically consecutive (the IPU processing unit is required), and the Android syst

Copy_to_user needs to check the validity of the pointer during each copy, that is, the pointer to the address of the user space is indeed the address of the process itself, instead of pointing to the location that does not belong to it, in addition, data is copied once each time, and memory is frequently accessed. Because the virtual address is continuous, the physical address may not necessarily be consecutive, resulting in frequent cache failures of the CPU, thus reducing the speed.MMAP only c

View MySQL LogsInnodb:initializing buffer pool, size =128.0MInnodb:mmap (137363456bytes) failed; Errno Ainnodb:completed Initialization of buffer poolinnodb:fatal Error:cannot allocate memory forThe buffer Pool[error] Plugin'InnoDB'Initfunctionreturned error. [ERROR] Plugin'InnoDB'registration as a STORAGE ENGINE failed. [ERROR] Unknown/Unsupported storage engine:innodb[error] abortingToo few caches. free-m total used free shared buffers Cachedmem: 11

Shared memory can be said to be the most useful interprocess communication and the fastest form of IPC because processes can read and write directly to memory without requiring any copy of the data. For communication like pipelines and Message Queuing, four copies of the data are required in the kernel and user space, while shared memory copies only two times: one from the input file to the shared memory area and the other from the shared memory area

# include 16 # include 17 # include 18 # include 19 20 21 # define DEVICE_NAME "mymap" 22 23 24 static unsigned char array [10] = {0, 1, 3, 4, 5, 6, 7, 8, 9}; 25 static unsigned char * buffer; 26 27 28 static int my_open (struct inode * inode, struct file * file) 29 {30 re

I. overview memory ing: in short, you can map a memory area of your space to the kernel space. After the ing is successful, your modifications to this memory area can be directly reflected in the kernel space. On the contrary, modifications made to

Recently in doing video output related things, for reserved for framebuffer memory use is not very clear, now find some information to tidy up, in case of use.For a system, there will be a lot of peripherals, then the management of these peripherals

Overview of Shared memory The shared memory area is the fastest form of IPC, where data delivery is no longer related to the kernel, in other words, processes no longer pass data to each other by executing system calls into the kernel. That is,

    Ffi = require 'ffi' ffi. cdef [[ int open (const char * file, int flag); void * mmap (void * _ addr, int _ len, int _ prot, int _ flags, int _ fd, int _ offset); # pragma pack (1) typedef struct { char name [21]; unsigned short age;

implemented differently, but its basic form is:struct stat{Mode St_mode; /* File type and mode (license number) * *Ino st_ino;/* I-node number (serial number) * *Dev st_dev;/* Equipment Number (file system) */Dev st_rdev;/* device number for special file * *Nlink st_nlink;/* Connection Number * *UID st_uid;/* owner's user id*/GID st_gid;/* Group id*/Off st_size;

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: i

;d_name.name #endif #if linux_version_code >= 0x020616 p->mm->mmap- Gt;vm_file->f_path.dentry->d_name.name #else P->mm->mmap->vm_file->f_dentry->d_name.name # endif You can get "test" in "/home/yaog/test", and then based on [CPP] view plain copy print? #if linux_version_code >=0x020616 p->mm->mmap->vm_file->f_path.dentry->d_parent #else P->MM-G T;

, loff_t *); ssize_t (* aio_write) (struct kiocb *, const char _ User*, Size_t, loff_t); int (* readdir) (struct file *, void *, filldir_t );Unsigned int (* poll) (struct file *, struct poll_table_struct *); int(* IOCTL) (struct inode *, struct file *, unsigned int, unsigned long); long(* Unlocked_ioctl) (struct file *

File type, C language file read/write, File Buffer, file opening method, file operation functionFile types include stream files and device files. device files such as VGA interfaces, serial ports, USB ports, network ports, and serial ports are abstracted into files by the op