Allocating memory in C# is not actually allocating memory

c# allocate memory
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When I declare a new byte array, the memory usage does not increase.

byte[] test = new[1024*100];

Its only after I iterate through each byte does it actually start taking ram.

How can I make it actually commit the memory without having to use it first?

I am using this as a test with a try catch block to see if it will fail to allocate the memory, thus telling me that my application is out of ram and it should not attempt to allocate any new objects.

Edit: since the objects I am going to be allocating are used with the garbage collector and stack, I don't want to allocate using malloc since it might succeed there, but fail when trying to allocate a new managed object.

Well, if you really want to map all that memory, then reiterate through the array and fill it with zeroes. It's linear time anyway. Use Array.Clear for that. C# really isn't made for such memory optimization in mind. The only resources you should be ever caring about are unamaged resources. The correct way of thinking about the rest of memory consumption in C# is not thinking about it at all. I honestly had no idea how C# handles memory allocation during an array declaration, and that's kinda the point, I'm not using a high-level abstract language to care about such stuff. It only makes sense if you have a working application that encounters a memory bottleneck and you need to optimize.

There is a stackalloc operator, which you could maybe bend to your use, but it's an unsafe operator. Also there is GC.GetTotalMemory(), which can show you the current memory usage (of managed objects), and Microsoft.VisualBasic.Devices.ComputerInfo.TotalPhysicalMemory which will give you the total RAM of the machine (don't mind the VB in the name, it's a .NET Framework method, just add a reference to Microsoft.VisualBasic.Devices), so using this you could achieve your goal of knowing more or less if there's enough memory for you to allocate your array.

arrays, Well, if you really want to map all that memory, then reiterate through the array and fill it with zeroes. It's linear time anyway. Use Array.Clear for  USING STRINGBUILDER CLASS DOES NOT ENSURE THAT A STRING IS ALLOCATE IN THE GLOBAL KERNEL MEMORY. THAT'S WHAT MY LATEST POST IS ABOUT. In this case, the GLOBAL MEMORY ALLOCATION itself is a slightly different topic. The memory allocated during an MS-Excel file creation is allocated on the server side in the MS-Excel application process.

If you want it to allocate all of the bytes, you can use Array.Clear, it will fill all values with 0

Array.Clear(test, 0, test.Length);

This simple console app lets you monitor the memory usage as it's created and populated with clear

class Program
    static void Main(string[] args)
        //Memory usage 7.1 MB
        Console.WriteLine("Hit enter to allocate");
        byte[] data = new byte[1024*1024]; //Memory still 7.1 MB
        Console.WriteLine("Hit Enter to Fill with zeros!");
        Array.Clear(data, 0, data.Length); //Memory now 8.1 MB
        Console.WriteLine("1MB filled, hit enter to exit");

Increasing performance via low memory allocation in C#, Increasing performance via low memory allocation in C# Not only this, but each time a garbage collection is triggered, much of the work is As it turned out, I was actually running into a detail about how lists work in C#. Then when will the memory be allocated? The answer is "when we use it in an array in our program". Actually the .NET code optimizer is very smart when it sees that there is no use of an array in the current program, it simply omits the array from being processed. Is it really? Hmm, are you not believing me? Look at the next screen.

Made a function that will attempt to actually allocate the memory I specify (and throw an exception if its not possible rather than lie about it) and will be instantly collected by the garbage collector if it succeeds.

bool IsMemoryAvailable(int amount)
    int size = (int)Math.Sqrt(amount) / 2;

        using (Bitmap bmpTest = new Bitmap(size, size))



        return true;
    catch(Exception x)
        return false;

Breaking down the fundamentals of C #: allocating memory for a , NET,; C#. Translation. This article will show you the basics of types internals, as of course an example in Actually, that's all. You should not use it in real projects, the method allocating memory on the stack uses new T ()  Re: De-Allocate Dictionary Memory in C# best practice May 07, 2014 11:56 AM | AidyF | LINK Believe it or not, but setting to null can actually delay how long it takes for memory to be reclaimed rather than speeding it up.

Saving Memory with C# Structs, Class instances in C# are always allocated on the heap! A struct in C# is referred to as a value type. Variables of this type are not pointers, but the objects themselves. If you create a struct as a function-local variable, its memory will be allocated on the stack. Oh my. Only 33% CPU utilization, and only four of the cores are actually doing anything. So, we've learned that, as with C++, the memory management in .NET is blocking when we allocate memory. No big surprise, really. By the way, the memory allocation never exceeded about 1GB.

Finalizing Objects, and Memory Concepts (Stack versus Heap), The stack is a memory object allocated when a program begins execution, and reason why reference data types are allocated on the heap, and not the stack. For C# applications, the heap is actually a "managed" heap, meaning that all  Dynamic memory allocation is the process of assigning the memory space during the execution time or the run time. Reasons and Advantage of allocating memory dynamically: When we do not know how much amount of memory would be needed for the program beforehand. When we want data structures without any upper limit of memory space.

Comparing Memory Allocation Methods, For example, HeapAlloc can be instructed to raise an exception if memory could not be allocated, a capability not available with LocalAlloc. This is the third part of the Custom memory allocation series. For your convenience you can find other parts in the table of contents in Part 1 — Allocating object on a stack. Hi! We already know how to allocate objects on a stack, we also evaluated the performance of list storing objects instead of references.

  • @maccettura I don't want unmanaged memory
  • Use special viewers such as Process Exporer and you will see this does allocate memory. It doesn't show in commited but once you iterate check the commited go up. You cannot allocate more than 2 gb to 1 object IIRC
  • @John could you try to change the value of the last element to ensure the array memory is allocated??
  • @John What is the problem that you are actually trying to solve? (Your question is based on a mistaken observation: the memory is actually committed when you create your array, but that's besides the point.)
  • @John just allocate the array as needed - if you're running out of memory, it'll fail. Arrays are allocated in one continuous block so be aware that you may have enough memory in several smaller blocks but not in a single massive block. Your problem still sounds like an X-Y problem, though - if you definitely know you criitcally need that much memory, you should reserve it and use your own memory manager.
  • "commit" is the wrong word, the address space is committed after new and the OS has reserved space for the allocation in the paging file. "mapped" is the better word.
  • If I fill all the bytes of the array I allocate, it takes over 500 milliseconds which is much to slow when I need to be less than 16 milliseconds for every function call. I tried setting the last element to a value to see if it would allocate the physical pages so the test would work, but it seems to not work. Also since the garbage collector doesn't take the byte array when I do GC.Collect(), it causes the test to fail and when I go to allocate a Bitmap later in my application, it throws a out of memory Exception.
  • @John No way, will it take 500ms just to fill an array. How do you fill your array and how did you measure it?
  • Calling clear fills the array with zeroes and allocated the memory. You can see it happen watching the ram. It really sounds like you are using the wrong tool for the job. If you need this kind of explicit memory management than you should be managing it yourself. Also, why does your program need to allocate so much memory at one time? Can’t resources be released and memory reused?
  • @ckuri he is allocating in the gigabyte range. 7 mb in the example is fine but 1 gb is very slow.
  • Explicitly calling gc.collect is not recommended.…
  • @bhmahler its absolutely required, otherwise it will not release the memory that was just allocated and when other legitimate calls to allocate a new object will fail throughout the application.
  • That’s not true. When you use a using the object is disposed when you exit. That tells the garbage collector that it is ready for removal and it will do so when needed. Do some more research on the garbage collector in .net
  • @bhmahler test my original question's code yourself and let me know when you confirmed how wrong you are.