For most architectures, the holes have entries in the memmap array. In the FLATMEM memory model, there is a global memmap array that maps the entire physical memory. This model is suitable for non-NUMA systems with contiguous, or mostly contiguous, physical memory. Vmalloc uses a dynamic mapping, on demand. FLATMEM The simplest memory model is FLATMEM. This mapping is built during boot, and is never changed. virtual address X is mapped to physical address X-C (where C is some constant, e.g. Lowmem uses a 1-1 mapping between virtual and physical addresses. Get Understanding the Linux Kernel, Second Edition now with the O’Reilly learning platform. svg then the template Vector version available (or Vva) does not need the new image name parameter. 2 Answers Sorted by: 58 busybox devmem busybox devmem is a tiny CLI utility that mmaps /dev/mem. Linux divides the kernel virtual address space to two parts - lowmem and vmalloc. Once the mapping is created, the process can read the data stored in the file by simply reading from the memory locations of. Programmers must specify either the MAP_SHAREDįlag or the MAP_PRIVATE flag as a parameter of the system call as you can easily guess, in the former case the mapping is shared, while in the latter it is private. Several of the map types exist to support specific BPF helpers that perform actions based on the map contents. There are several storage types available, including hash, array, bloom filter and radix-tree. Mmap( ) system call (see Section 15.2.2 later in this chapter). BPF 'maps' provide generic storage of different types for sharing data between kernel and user space. To any other processes that access the same file.Ī process can create a new memory mapping by issuing an Thus,Ī write does not change the file on disk, nor is the change visible Mapped page will cause it to stop mapping the page in the file. For this purpose, private mapping is moreĮfficient than shared mapping. To be used when the process creates the mapping just to read theįile, not to write it. Mapping, the changes are visible to all other processes that map the Write operation on the pages of the memory region changes the file onĭisk moreover, if a process writes into a page of a shared memory

Linux kernel map