Question

We’re currently preparing our Azure role (standard Web Role) for an expected massive load, and we need to know how much memory the current setup consumes. To accomplish this, we’re using load tests while measuring the consumed memory with GC.GetTotalMemory.

The page http://technet.microsoft.com/en-us/cloud/gg663909.aspx lists the Compute Instance Guaranteed Memory for each instance size (for example, 0.768 GB for the Extra-Small Instance and 3.5 GB for the Medium Instance).

Are the values of GC.GetTotalMemory comparable to the values in these list? In other words, if GC.GetTotalMemory is staying significantly below the listed limit, can we be sure that there won’t be any sudden perfomance loss due to memory swapping?

If we hit the limit, is our assumption correct that there will be some memory swapping (writing memory content to the virtual harddisk), or will there be more severe implications like repeated App Pool recycling?

(the last question comes up because most shared hosters will recycle your App Pool if you hit some memory limit, but frankly we don’t expect anything like this from Windows Azure)

Answer 1

This method will only give you the currently allocated bytes by your process. The 0.768 GB includes the memory availble to the operating system, and there can be virtual memory as well.

system.gc.gettotalmemory

To get the total system memory you can use:

Add a Reference to System.Management.

private static void DisplayTotalRam()
{
  string Query = "SELECT MaxCapacity FROM Win32_PhysicalMemoryArray";
  ManagementObjectSearcher searcher = new ManagementObjectSearcher(Query);
  foreach (ManagementObject WniPART in searcher.Get())
  {
    UInt32 SizeinKB = Convert.ToUInt32(WniPART.Properties["MaxCapacity"].Value);
    UInt32 SizeinMB = SizeinKB / 1024;
    UInt32 SizeinGB = SizeinMB / 1024;
    Console.WriteLine("Size in KB: {0}, Size in MB: {1}, Size in GB: {2}", SizeinKB, SizeinMB, SizeinGB);
  }
}

Source for code