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Object size in memory

P: n/a
I need to get the size of an objet in memory. I have tried:

System.IO.MemoryStream m = new System.IO.MemoryStream();

System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter b = new
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter();
b.Serialize(m, Obj);
double size = Convert.ToDouble(m.Length);

but not everything is serializable. The thing is I want to be able to
take an arbitarty object, (since everything I am attempting to size is
comming out of the cache), and get the size of it. I am wondering if it
not possible to treat it like a stream or a byte array or something like
that so that it is easy to get the size. I don't need any attributes off
of the object, I just need the size. Anyone have any ideas?

-Cam

Nov 15 '05 #1
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6 Replies

P: n/a
cameron <ca****************@appdepot.com> wrote:
I need to get the size of an objet in memory. I have tried:

System.IO.MemoryStream m = new System.IO.MemoryStream();

System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter b = new
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter();
b.Serialize(m, Obj);
double size = Convert.ToDouble(m.Length);

but not everything is serializable. The thing is I want to be able to
take an arbitarty object, (since everything I am attempting to size is
comming out of the cache), and get the size of it. I am wondering if it
not possible to treat it like a stream or a byte array or something like
that so that it is easy to get the size. I don't need any attributes off
of the object, I just need the size. Anyone have any ideas?


"Size" can be either misleading or meaningless when you consider
reference types. For instance:

public class Foo
{
string x;

public Foo (string x)
{
this.x=x;
}
}
Foo f1 = new Foo ("hello");
Foo f2 = new Foo ("hello");

Now, what is the size of f1 and f2? Combined, it should be double the
size of the Foo class instance itself (probably 12 bytes - an object
header of 8 bytes plus a reference) and the size of the string (16 or
20 bytes, at a guess) - but the size of each of them individually would
be the size of the Foo class instance itself plus the string - so the
whole is greater than the sum of the parts... but if you ignore the
string itself, it becomes meaningless in the other way.

So, what do you *really* mean, and what do you *really* want to try to
measure?

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Nov 15 '05 #2

P: n/a
Hi cameron,
Serialization won't help. First because it will put more info than you maybe
expect. The stream is goint to be bigger then the object itself is. Second
because serializer (if you don't take any precautios) will serialize any
serializable objects your object references.

IMHO there is no way to get the size of a managed object. Even the size
might not be the same if you run the application on machines with different
configuration and/or different versions of .NET. If not stated otherways CLR
is free to rearange and layout the objects as it sees fit. That means that
you may end up with diffrent padding of the fields and different sizes in
memory.

The only size that you can get is the size on bytes of the unmanaget
equivalent of your type
Marshal.SizeOf(...)
--
B\rgds
100

"cameron" <ca****************@appdepot.com> wrote in message
news:%2******************@tk2msftngp13.phx.gbl...
I need to get the size of an objet in memory. I have tried:

System.IO.MemoryStream m = new System.IO.MemoryStream();

System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter b = new
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter();
b.Serialize(m, Obj);
double size = Convert.ToDouble(m.Length);

but not everything is serializable. The thing is I want to be able to
take an arbitarty object, (since everything I am attempting to size is
comming out of the cache), and get the size of it. I am wondering if it
not possible to treat it like a stream or a byte array or something like
that so that it is easy to get the size. I don't need any attributes off
of the object, I just need the size. Anyone have any ideas?

-Cam

Nov 15 '05 #3

P: n/a
Fair enough. The Object is being placed in the Cache - I want to know
how much space is being taken up by that object, (in it's entirity), on
the Heap.

-Cam

Jon Skeet [C# MVP] wrote:
cameron <ca****************@appdepot.com> wrote:
I need to get the size of an objet in memory. I have tried:

System.IO.MemoryStream m = new System.IO.MemoryStream();

System.Runtime.Serialization.Formatters.Binary.B inaryFormatter b = new
System.Runtime.Serialization.Formatters.Binary.B inaryFormatter();
b.Serialize(m, Obj);
double size = Convert.ToDouble(m.Length);

but not everything is serializable. The thing is I want to be able to
take an arbitarty object, (since everything I am attempting to size is
comming out of the cache), and get the size of it. I am wondering if it
not possible to treat it like a stream or a byte array or something like
that so that it is easy to get the size. I don't need any attributes off
of the object, I just need the size. Anyone have any ideas?

"Size" can be either misleading or meaningless when you consider
reference types. For instance:

public class Foo
{
string x;

public Foo (string x)
{
this.x=x;
}
}
Foo f1 = new Foo ("hello");
Foo f2 = new Foo ("hello");

Now, what is the size of f1 and f2? Combined, it should be double the
size of the Foo class instance itself (probably 12 bytes - an object
header of 8 bytes plus a reference) and the size of the string (16 or
20 bytes, at a guess) - but the size of each of them individually would
be the size of the Foo class instance itself plus the string - so the
whole is greater than the sum of the parts... but if you ignore the
string itself, it becomes meaningless in the other way.

So, what do you *really* mean, and what do you *really* want to try to
measure?


Nov 15 '05 #4

P: n/a
cameron <ca****************@appdepot.com> wrote:
Fair enough. The Object is being placed in the Cache - I want to know
how much space is being taken up by that object, (in it's entirity), on
the Heap.


Right - as I said, that really depends on other objects etc. There's no
way of determining it, I'm afraid. If you know more about your objects
- like that the bulk of the size is going to be taken up by a byte
array which you have access to and which won't have duplicate
references within the cache, for instance, you could use the size of
that as a rough indication...

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Nov 15 '05 #5

P: n/a

Hi cameron,

Thank you for posting in the community!

I think Stoitcho and Jon have explained the reason why you can not get the
managed class instance size.

But I think what you want to do is getting the unmanaged class instance
size, so just as Stoitcho point out, you can use Marshal.SizeOf to returns
the unmanaged size of an object in bytes.

For more information, please refer to:
http://msdn.microsoft.com/library/de...us/cpref/html/
frlrfsystemruntimeinteropservicesmarshalclasssizeo ftopic.asp

==========================================
Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

Nov 15 '05 #6

P: n/a

Hi cameron,

Does the community's reply make sense to you?

If you still have anything unclear, please feel free to post, we will help
you.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

Nov 15 '05 #7

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