From IEEE 1003.1: The mmap() function shall establish a mapping between a process’ address space and a file, shared memory object, or [TYM] typed memory object. It needs all the virtual address space because that’s exactly what mmap() does. The fact that it isn’t really running out of memory doesn’t matter – you can’t map … Read more
The real answer is to use a crate that provides this functionality, ideally in a cross-platform manner. use memmap; // 0.7.0 use std::{ fs::OpenOptions, io::{Seek, SeekFrom, Write}, }; const SIZE: u64 = 1024 * 1024; fn main() { let src = “https://stackoverflow.com/questions/28516996/Hello!”; let mut f = OpenOptions::new() .read(true) .write(true) .create(true) .open(“test.mmap”) .expect(“Unable to open file”); … Read more
Both methods are viable. 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 … Read more
I’d redesign this to act streaming, instead of on a block. A simpler approach would be: std::ifstream ifs(“input.txt”); std::vector<uint64_t> parsed(std::istream_iterator<uint64_t>(ifs), {}); If you know roughly how many values are expected, using std::vector::reserve up front could speed it up further. Alternatively you can use a memory mapped file and iterate over the character sequence. How to … Read more
Is it possible to attach that region of memory to the server POST forking, after the client creates it? MAP_ANONYMOUS|MAP_SHARED mapped memory can only be accessed by the process which does that mmap() call or its child processes. There is no way for another process to map the same memory because that memory can not … Read more
MAP_PRIVATE mappings require a memory reservation, as writing to these pages may result in copy-on-write allocations. This means that you can’t map something too much larger than your physical ram + swap. Try using a MAP_SHARED mapping instead. This means that writes to the mapping will be reflected on disk – as such, the kernel … Read more
What are the different ways I can write in kernel address space from user space? I’m not sure if there’re other methods, but you can access physical memory using /dev/mem & system call mmap(). /dev/mem is a character device file that is an image of the main memory of the computer. It may be used, … Read more
If you are using MAMP be sure to add the unix_socket key with a value of the path that the mysql.sock resides in MAMP. ‘mysql’ => array( ‘driver’ => ‘mysql’, ‘host’ => ‘localhost’, ‘unix_socket’ => ‘/Applications/MAMP/tmp/mysql/mysql.sock’, ‘database’ => ‘database’, ‘username’ => ‘root’, ‘password’ => ‘root’, ‘charset’ => ‘utf8’, ‘collation’ => ‘utf8_unicode_ci’, ‘prefix’ => ”, ),
I think I’ve found the issue — it’s to do with /dev/mem memory mapping protection on the x86. Pl refer to this LWN article: “x86: introduce /dev/mem restrictions with a config option” http://lwn.net/Articles/267427/ CONFIG_NONPROMISC_DEVMEM Now (i tested this on a recent 3.2.21 kernel), the config option seems to be called CONFIG_STRICT_DEVMEM. I changed my kernel … Read more