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- linux - How does mmap work? - Stack Overflow
mmap works by manipulating your process's page table, a data structure your CPU uses to map address spaces The CPU will translate "virtual" addresses to "physical" ones , and does so according to the page table set up by your kernel
- memory - Understanding mmap - Unix Linux Stack Exchange
What's actually happening in most cases is that mmap() is providing copy-on-write access to that file's data in the page cache As a result, the usual cache restrictions on data lifetime apply: if the system needs space, pages can be dropped (or flushed to disk if they're dirty) from the cache and need to be faulted in again
- c - When should I use mmap for file access? - Stack Overflow
One place mmap can be awkward is if you need to work with very large files on a 32 bit machine This is because mmap has to find a contiguous block of addresses in your process's address space that is large enough to fit the entire range of the file being mapped This can become a problem if your address space becomes fragmented, where you
- c - What does mmap do? - Stack Overflow
man mmap will help you here It creates a memory mapping in the virtual address space of the process It's creating an anonymous mapping, which is rather like using malloc to allocate n bytes of memory The parameters are: NULL - the kernel will choose an address for the mapping; n - length of the mapping (in bytes) PROT_WRITE - pages may be
- malloc vs mmap in C - Stack Overflow
The mmap code is faster because for your program, mmap has resulted in either less disk access, or more efficient disk access, than whatever reads and writes you compared against For instance, write ing the whole file actually sends all those bytes to disk mmap just means if you modify the mmap ed data, then the OS will write the changes So
- c - Linux shared memory: shmget() vs mmap()? - Stack Overflow
mmap method is a little bit more restrictive then shmget, but easier to use shmget is the old System V shared memory model and has the widest support mmap shm_open is the new POSIX way to do shared memory and is easier to use If your OS permits the use of POSIX shared memory then I would suggest going with that
- c++ - mmap() vs. reading blocks - Stack Overflow
mmap doesn't require a copy of the file data from kernel to user-space mmap allows you to access the file "as memory", including processing it with whatever advanced tricks you can do against memory, such as compiler auto-vectorization, SIMD intrinsics, prefetching, optimized in-memory parsing routines, OpenMP, etc
- c - When would you use mmap - Stack Overflow
mmap can also be used for an anonymous mapping This mapping is not backed by a file, and is basically a request for a chunk of memory If that sounds similar to malloc, you are right In fact, most implementations of malloc will internally use an anonymous mmap to provide a large memory area
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