mmap

I am developing for an ARM device running Linux 2.6.37. I am trying to toggle an IO pin as fast as possible. I made a little kernel module and a user space application. I tried two things : Manipulate the GPIO control registers directly from the kernel space using ioremap . mmap() the GPIO control registers without caching and using them from user space. Both methods work, but the second is about 3 times slower than the first (observed on oscilloscope). I think I disabled all caching mechanisms. Of course I'd like to get the best of the two worlds : flexibility and ease of development from

java 版的 mmap，返回的对象是 DirectByteBuffer，是堆外内存 // java.nio.channels.FileChannel#map public abstract MappedByteBuffer map(MapMode mode, long position, long size) throws IOException; 设置堆外内存的大小 -XX:MaxDirectMemorySize=16G 来源： https://www.cnblogs.com/allenwas3/p/11757237.html

I'm trying to map an array to a file via Mmap, the array could be any type, like float64. In C, I find this one . After reading some texts, I wrote this sample . I don't know if it is correct, and it is not writing the values to the file. If I increase the size of array a lot, e.g from 1000 to 10000, it crashes. If someone know how to do that in the correctly way, please, tell me. Thanks! For example, revising your sample program, package main import ( "fmt" "os" "syscall" "unsafe" ) func main() { const n = 1e3 t := int(unsafe.Sizeof(0)) * n map_file, err := os.Create("/tmp/test.dat") if err !

Just the question stated, how can I use mmap() to allocate a memory in heap? This is my only option because malloc() is not a reentrant function. Why do you need reentrancy? The only time it's needed is for calling a function from a signal handler; otherwise, thread-safety is just as good. Both malloc and mmap are thread-safe. Neither is async-signal-safe per POSIX. In practice, mmap probably works fine from a signal handler, but the whole idea of allocating memory from a signal handler is a very bad idea. If you want to use mmap to allocate anonymous memory, you can use (not 100% portable but

I am writing a program that allocates huge chunks of memory using mmap and then accesses random memory locations to read and write into it. I just tried out the following code: #include <stdio.h> #include <stdlib.h> #include <sys/mman.h> int main() { int fd,len=1024*1024; fd=open("hello",O_READ); char*addr=mmap(0,len,PROT_READ+PROT_WRITE,MAP_SHARED,fd,0); for(fd=0;fd<len;fd++) putchar(addr[fd]); if (addr==MAP_FAILED) {perror("mmap"); exit(1);} printf("mmap returned %p, which seems readable and writable\n",addr); munmap(addr,len); return 0; } But I cannot execute this program, is there anything