memory-mapping

I'm using PCI-e port on Freescale MPC8308 processor (which is based on PowerPC architecture) and I have some problems when trying to use it. The endpoint PCI-e device has memory space equal to 256 MB. I can easily read and write configuration space of the endpoint device by using "pciutils" package. After writing correct values in configuration registers and getting the permission to access the memory space; I tried to access memory space by using "mmap()" function in C and used the file descriptor located at : "/sys/devices/pci0000:00/0000:00:00.0/resource0" which was exactly 256 MB (equal to

There exists the mmap module for node.js: https://github.com/bnoordhuis/node-mmap/ As the author Ben Noordhuis notes, accesing mapped memory can block, which is why he does not recommend it anymore and discontinued it. So I wonder how would I design a non-blocking memory mapping module for node.js? Threading, Fibers, ? Obviously this nearby raises the question if threading in node.js would just happen elsewhere instead of the request handler. josh3736 When talking about implementing some native facility in a non-blocking fashion, the first place to look is libuv . It is how node's core modules

I can read/write a linux block device with Java using java.nio . The following code works: Path fp = FileSystems.getDefault().getPath("/dev", "sdb"); FileChannel fc = null; try { fc = FileChannel.open(fp, EnumSet.of(StandardOpenOption.READ, StandardOpenOption.WRITE)); } catch (Exception e) { System.out.println("Error opening file: " + e.getMessage()); } ByteBuffer buf = ByteBuffer.allocate(50); try { if(fc != null) fc.write(buf); } catch (Exception e) { System.out.println("Error writing to file: " + e.getMessage()); } However, memory mapping does not work. The following code fails :

I sometimes see statements that on some platforms the following C or C++ code: int* ptr; *ptr = 0; can result in writing to a hardware input-output port if ptr happens to store the address to which that port is mapped. Usually they are called "embedded platforms". What are real examples of such platforms? Most systems in my experience use memory-mapped I/O. The x86 platform has a separate, non-memory-mapped I/O address space (that uses the in / out family of processor op-codes), but the PC architecture also extensively uses the standard memory address space for device I/O, which has a larger

I have recently discovered that Linux does not guarantee that memory allocated with mmap can be freed with munmap if this leads to situation when number of VMA (Virtual Memory Area) structures exceed vm.max_map_count . Manpage states this (almost) clearly: ENOMEM The process's maximum number of mappings would have been exceeded. This error can also occur for munmap(), when unmapping a region in the middle of an existing mapping, since this results in two smaller mappings on either side of the region being unmapped. The problem is that Linux kernel always tries to merge VMA structures if

I am trying to build a distributive computing system that uses memory mapping files to coordinate work among several networked PCs all via VBA. Put another way, I want to get a group of networked computers to do work at the same time in a coordinated way on a single project that can be easily divided up into different parts. One PC takes 13+ hours to complete the project, which is not practical for my client. I want to store information in the memory mapping files that will help the PCs work on the project in a coordinated way (i.e. no duplication of work, avoid race issues, etc). I've tried