I have an empty object, I have created instance of type MyCustomType and compiled my application(x64 platform). Then I wonder how many bytes does my type hold. I opened .NET memory profiler and accordint to it, my type weight is - 24 bytes. So I know that in x64 platform any reference type in .NET has overhead - 16 bytes. Doubdless 16 != 24. And my question is: where other 8 bytes?
Thanks!
internal class MyCustomType
{
}
1 - There’s a "base" overhead of 8 bytes per object in x86 and 16 per object in x64… given that we can store an Int32 of "real" data in x86 and still have an object size of 12, and likewise we can store two Int32s of real data in x64 and still have an object of x64.
2 - There’s a "minimum" size of 12 bytes and 24 bytes respectively. In other words, you can’t have a type which is just the overhead. Note how the "Empty" class takes up the same size as creating instances of Object… there’s effectively some spare room, because the CLR doesn’t like operating on an object with no data. (Note that a struct with no fields takes up space too, even for local variables.)
3 - The x86 objects are padded to 4 byte boundaries; on x64 it’s 8 bytes (just as before)
4 - By default, the CLR is happy to pack fields pretty densely – Mixed2 only took as much space as ThreeInt32. My guess is that it reorganized the in-memory representation so that the bytes all came after the ints… and that’s what a quick bit of playing around with unsafe pointers suggests too… but I’m not sufficiently comfortable with this sort of thing to say for sure. Frankly, I don’t care… so long as it all works, what we’re interested in is the overall size, not the precise layout.
http://codeblog.jonskeet.uk/2011/04/05/of-memory-and-strings/