Any day now we will have the first snow of the season. People are busy putting up lights and Christmas trees. The shopping centers are full of eager shoppers. Now you might be saying to yourself, that we already have access to shared memory areas via the import and export statements.
NET 4, beyond the most popular ones like dynamic types and covariance; I was interested in performance enhancements. For this reason I am going to publish a couple of blog entries were I explore these different features.
Memory mapped files may sounds alien to the managed code developer but it has been around for years, what is more, it is so intrinsic in the OS that practically any communication model that wants to share data uses it behind the scenes. So what is it?
I will say that it has two main purposes: This works great when you deal with large data files. The memory mapped file is the most efficient way for multiple processes on a single machine to communicate with each other.
What is more, if we check other IPC methods we can see the following architecture: Now you have the power of this technology available on the System. IO namespace instead of using the Pinvoke approach. We have two types of memory mapped files models, one model is using a custom file, this can be any file that the application accesses it and the other one using the page file that we are going to share it with the memory manager this is the model that most of the technologies above use.
The first thing that we need to do is to create a FileStream to the file that we are going to use, this can be an existing file or a new file keep in mind that you should open this file as shared, otherwise no other process will be able to access it!
With the stream in place, we can now create the memory mapped file.Run it twice from two distinct command prompts: the first instance creates the shared memory, the second one writes a message into it.
BTW: created with C++ Builder. If you're using MSVC, just remove #include and #pragma hdrstop and it should compile. It's the loneliness of it. Memories need to be shared.” ― Lois Lowry, The Giver. tags: loneliness, memories, pain, share. likes. Like “No matter how much suffering you went through, you never wanted to let go of those memories.” “He was still too young to know that the heart's memory eliminates the bad and magnifies the good.
He who has gone, so we but cherish his memory, abides with us, more potent, nay, more present than the living man. Antoine de Saint-Exupery Death leaves a heartache no one can heal, love leaves a memory no one can steal.
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, closer to a processor core, which stores copies of the data from frequently used main memory .
This paper introduces the queue-read queue-write (qrqw) parallel random access machine (pram) model, which permits concurrent reading and writing to shared-memory locations, but at a cost proportional to the number of readers/writers to any one memory location in a given step.
Since this database is in-memory, we don't care about write amplification. We do, however, care a lot about read amplification and space amplification. This is an interesting example because we tune the compaction to an extreme so that usually only one SST table exists in the system.