6/19/2023 0 Comments Memory mapped file![]() ![]() Here is a Python code snippet that demonstrates the use of memory mapped files. Behind the scenes, named pipes may implement an IPC shared memory. ![]() ![]() It is based on client server communication model with a sender and a listener. Named pipes allow one process to communicate with another process in real time on the same computer or through a network.Moreover, IPC can be implemented using memory mapped file technique, however it is not as fast as a pure memory only IPC.Shared memory is a RAM only form of interprocess communication (IPC) that does not require disk operations.Expanding file size is not easy to implement because a memory mapped file is assumed to be fixed in size.ĭifference between memory mapped file and shared memory.In other words, user applications have no control over memory allocation. Memory footprint is larger than that of traditional file IO.Recall that accessing file in memory may generate a lot of page faults which is bad. The notion that a memory mapped file has always better performance should not be taken for granted.Memory mapping text files is not such an appealing task as it may require proper text handling and conversion.Memory mapping is generally good for binary files, however reading formatted binary file types with custom headers such as TIFF can be problematic.Just like any other technique, memory mapping has some drawbacks. Simplicity: dealing with memory as opposed to allocating space, copying data and deallocating space.Sharing: facilitates data sharing and interprocess communication.Fast: accessing virtual memory is much faster than accessing disk.Efficiency: when dealing with large files, no need to read the entire file into memory first.Memory mapping is an excellent technique that has various benefits. If you are curious to know why? please leave a comment in the comments section at the end of this post. There is a rational behind each example in the list above. When the file contains data of great importance to the application.Sharing a file or a portion of a file between multiple applications.Loading a small file once then randomly accessing the file frequently.Randomly accessing a huge file once (or a couple of times).Here are few scenarios where memory mapping is appealing. Is it a good option always? That is not necessarily the case. Memory mapped files sound like an efficient method to access files on disk. location within the file) that does not exists, a page fault occurs and the operating system brings the missing page into memory. The OS splits the memory mapped file into pages (similar to process pages) and loads the requested pages into physical memory on demand. This technique saves user applications IO overhead and buffering but it also has its own drawbacks as we will see later.īehind the scenes, the operating system utilizes virtual memory techniques to do the trick. It is obvious that accessing RAM is much faster than accessing disk via read and write system calls. Memory mapping refers to process ability to access files on disk the same way it accesses dynamic memory. Here are few articles that you may need to check out: Before we start, I recommend that you get a basic idea about some relevant concepts such as multitasking and paging. I will provide a short summary of memory mapped files in an easy to follow manner. Today, I am going to talk about memory mapping, a typical topic in operating systems design. ![]()
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