is it possible to know the memory occupation (bytes) of an object?

I once sent some code to the mailing list (search for thread named "Size of objects").

We should add this to the image. I think I named it #sizeInMemory.

Adrian

On Apr 27, 2010, at 12:03 , Mariano Martinez Peck wrote:

> Hi. I don't know if "memory occupation" is the better name. I just want to
> know the amount of memory that an object is occupying in RAM. I mean, the
> amount of bytes.
>
> Is this possible ? if true, how ?   I would like to do it from both sides:
> image and VM.
>
> I checked both but I didn't find anything.
>
> Thanks in advance
>
> Mariano

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BTW, Lukas had pointed out that my implementation is incomplete. So before integrating we should make sure the implementation covers all cases.

Adrian

Begin forwarded message:

> From: "Lukas Renggli" <[hidden email]>
> Date: October 21, 2008 6:28:32 PM GMT+02:00
> To: "Pharo Development" <[hidden email]>
> Subject: Re: [Pharo-project] Size of objects
> Reply-To: Pharo Development <[hidden email]>
>
>> BTW, I think that would be a meaningful addition. Could somebody quickly
>> check the method to verify that I didn't do any miscalculation?
>
> The only problem I see is that variable objects might also have
> inst-vars. So you need to count the
>
>    self class instSize * Smalltalk wordSize
>

> part in any case.
>
> Lukas

On Apr 27, 2010, at 12:45 , Adrian Lienhard wrote:

> I once sent some code to the mailing list (search for thread named "Size of objects"). We should add this to the image. I think I named it #sizeInMemory.
>
> Adrian
>
> On Apr 27, 2010, at 12:03 , Mariano Martinez Peck wrote:
>
>> Hi. I don't know if "memory occupation" is the better name. I just want to
>> know the amount of memory that an object is occupying in RAM. I mean, the
>> amount of bytes.
>>
>> Is this possible ? if true, how ?   I would like to do it from both sides:
>> image and VM.
>>
>> I checked both but I didn't find anything.
>>
>> Thanks in advance
>>
>> Mariano
>> _______________________________________________
>> Pharo-project mailing list
>> [hidden email]
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>
>
> _______________________________________________
> Pharo-project mailing list
> [hidden email]
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It's close but not entirely correct. The computation needs to include the extra header word for "large" instances (> 255 bytes). Squeak has three possible header sizes:

       1 header word  - used by compact classes
       2 header words - used by regular classes
       3 header words - used by "large" instances

BTW, SpaceTally>>spaceForInstancesOf:withInstanceCount: has the correct computation (except for 64 bit :-)

Is there a way to know this
but from the VM side also ? how ?
I really need it from the VM side :(  but I have no idea how to do it.

It's easy to do in the VM, just use this:

primitiveByteSize
       "Answers the number of bytes the receiver occupies"

       | nbytes|
       self export: true.
       oop := self popStack.
       nbytes := (self sizeBitsOf: oop) + (self extraHeaderBytes: oop).
       self pushInteger: nbytes.

It's close but not entirely correct. The computation needs to include the extra header word for "large" instances (> 255 bytes). Squeak has three possible header sizes:

       1 header word  - used by compact classes
       2 header words - used by regular classes
       3 header words - used by "large" instances

BTW, SpaceTally>>spaceForInstancesOf:withInstanceCount: has the correct computation (except for 64 bit :-)

Ok, perfect. Thanks :)

 

Is there a way to know this
but from the VM side also ? how ?
I really need it from the VM side :(  but I have no idea how to do it.

It's easy to do in the VM, just use this:

primitiveByteSize
       "Answers the number of bytes the receiver occupies"

       | nbytes|
       self export: true.
       oop := self popStack.
       nbytes := (self sizeBitsOf: oop) + (self extraHeaderBytes: oop).
       self pushInteger: nbytes.

I tried this and seems to work ok. I don't really need a primitive but an internal method that is called by a primitive. So, I did something like this:

internalByteSize: anOop

       "Answers the number of bytes the receiver occupies"
       | nbytes|

       self inline: true.
       nbytes := (self sizeBitsOf: anOop) + (self extraHeaderBytes: anOop).
       ^ nbytes.



and then I call it like this for example:

oop := self firstAccessibleObject.
    [oop = nil] whileFalse: [
        (self isIntegerObject:  oop)
            ifFalse: [
                size :=  self internalByteSize: oop.
           ......]
  oop := self accessibleObjectAfter: oop.
    ].

 
but internalByteSize ALWAYS return me the same value...do you know what can be wrong ?

Thanks in advance

Mariano

On 4/29/2010 6:22 AM, Mariano Martinez Peck wrote:

and then I call it like this for example:

oop := self firstAccessibleObject.
    [oop = nil] whileFalse: [
        (self isIntegerObject:  oop)
            ifFalse: [
                size :=  self internalByteSize: oop.
           ......]
  oop := self accessibleObjectAfter: oop.
    ].

Do you realize that this simple computes the used memory which is information that's directly accessible via the vm parameters? I don't recall which one but you might want to look at these to see if they already have what you need.

Cheers,
 - Andreas

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Its a simple method in Object:

Object>>sizeInMemory
       "Returns the number of bytes used by this object in memory (including its header)"

       | headerSize instanceSize |
       headerSize := (self class indexIfCompact > 0 ifTrue: [ 4 ] ifFalse: [ 8 ]).
       instanceSize := (self class isVariable
               ifFalse: [ self class instSize * Smalltalk wordSize ]
               ifTrue: [ (self basicSize * (self class isBytes
                       ifTrue: [ 1 ] ifFalse: [ Smalltalk wordSize ])) ]).
       ^ headerSize + instanceSize

Please also note the other mail I sent to this thread.

Adrian

On Apr 27, 2010, at 13:16 , Mariano Martinez Peck wrote:

> On Tue, Apr 27, 2010 at 12:45 PM, Adrian Lienhard <[hidden email]> wrote:
>
>> I once sent some code to the mailing list (search for thread named "Size of
>> objects").
>
>
> Thanks Adrian...I couldn't find it. Can you forward it to me please?  or
> just send me the code...
>
>
>> We should add this to the image. I think I named it #sizeInMemory.
>>
>>
> There are only changes to the image side ?  or the vm also ?
>
> Thanks
>
> Mariano
>
>
>
>> Adrian
>>
>> On Apr 27, 2010, at 12:03 , Mariano Martinez Peck wrote:
>>
>>> Hi. I don't know if "memory occupation" is the better name. I just want
>> to
>>> know the amount of memory that an object is occupying in RAM. I mean, the
>>> amount of bytes.
>>>
>>> Is this possible ? if true, how ?   I would like to do it from both
>> sides:
>>> image and VM.
>>>
>>> I checked both but I didn't find anything.
>>>
>>> Thanks in advance
>>>
>>> Mariano
>>> _______________________________________________
>>> Pharo-project mailing list
>>> [hidden email]
>>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>>
>>
>> _______________________________________________
>> Pharo-project mailing list
>> [hidden email]
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>>
> _______________________________________________
> Pharo-project mailing list
> [hidden email]
> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project


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On 21.09.2010 20:47, Mariano Martinez Peck wrote:

On Tue, Apr 27, 2010 at 1:19 PM, Adrian Lienhard <[hidden email]> wrote:

Its a simple method in Object:

Object>>sizeInMemory
       "Returns the number of bytes used by this object in memory (including its header)"

       | headerSize instanceSize |
       headerSize := (self class indexIfCompact > 0 ifTrue: [ 4 ] ifFalse: [ 8 ]).
       instanceSize := (self class isVariable
               ifFalse: [ self class instSize * Smalltalk wordSize ]
               ifTrue: [ (self basicSize * (self class isBytes
                       ifTrue: [ 1 ] ifFalse: [ Smalltalk wordSize ])) ]).
       ^ headerSize + instanceSize

Hi Adrian. Sorry for returning to this thread. I am trying to contemplate all the cases.

I was looking at SpaceTally and I found that maybe a better implementation could be something like this:

Object >> sizeInMemory
    "Answer the number of bytes consumed by this instance including object header."

    | isCompact instVarBytes bytesPerElement headerBytes total contentBytes |
    isCompact := self class indexIfCompact > 0.
    instVarBytes := self class instSize * 4.
    self class isVariable
        ifTrue: [
            bytesPerElement := self class isBytes ifTrue: [1] ifFalse: [4].
            total := 0.
            contentBytes := instVarBytes + (self basicSize * bytesPerElement).
                headerBytes :=
                    contentBytes > 255
                        ifTrue: [12]
                        ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].
                total :=  headerBytes + contentBytes.
            ^ total]
        ifFalse: [
            headerBytes :=
                instVarBytes > 255
                    ifTrue: [12]
                    ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].
            ^ headerBytes + instVarBytes ].



I guess I did some mistake but if we can arrive to a good implementation it would be really cool.

Thanks

mariano

Please, at least do some refactoring :)

Object >> sizeInMemory
    "Answer the number of bytes consumed by this instance including object header."

    | isCompact headerBytes contentBytes |

    isCompact := self class indexIfCompact > 0.

    contentBytes := self class instSize * Smalltalk wordSize. "inst vars"

    self class isVariable ifTrue:
        [ |bytesPerElement|
            bytesPerElement := self class isBytes ifTrue: [1] ifFalse: [4].

            contentBytes := contentBytes + (self basicSize * bytesPerElement)].

      headerBytes :=
                    contentBytes > 255
                        ifTrue: [12]
                        ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].

            ^ headerBytes + instVarBytes
 
Also, in a 64-bit image, I suspect you may have to make a distinction between class isWords as well.
ie:
self class isBytes ifTrue: [1] ifFalse: [self class isWords ifTrue: [4] ifFalse: [Smalltalk wordSize]]

Cheers,
Henry

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Some notes:

- What should be answered for small ints? 1 sizeInMemory -->8. That's wrong. Shouldn't this answer 0?

- In the line contentBytes := contentBytes + (self basicSize * bytesPerElement), why is contentBytes added because it should be always 0 because self class instSize should return 0 in case of variable classes. Or do I miss something?

- Please remove the inline comment "inst vars"; if a comment is needed it should go into the main comment.

Adrian

On Sep 21, 2010, at 22:14 , Mariano Martinez Peck wrote:

> 2010/9/21 Henrik Sperre Johansen <[hidden email]>
>
>> On 21.09.2010 20:47, Mariano Martinez Peck wrote:
>>
>>
>>
>> On Tue, Apr 27, 2010 at 1:19 PM, Adrian Lienhard <[hidden email]> wrote:
>>
>>> Its a simple method in Object:
>>>
>>> Object>>sizeInMemory
>>>       "Returns the number of bytes used by this object in memory
>>> (including its header)"
>>>
>>>       | headerSize instanceSize |
>>>       headerSize := (self class indexIfCompact > 0 ifTrue: [ 4 ] ifFalse:
>>> [ 8 ]).
>>>       instanceSize := (self class isVariable
>>>               ifFalse: [ self class instSize * Smalltalk wordSize ]
>>>               ifTrue: [ (self basicSize * (self class isBytes
>>>                       ifTrue: [ 1 ] ifFalse: [ Smalltalk wordSize ])) ]).
>>>       ^ headerSize + instanceSize
>>>
>>>
>       ^ headerSize + contentBytes
>
> :)
>
> Thanks Henry....so do you think we can integrate this?
>
> Adrian?
>
>
>
>>
>> Hi Adrian. Sorry for returning to this thread. I am trying to contemplate
>> all the cases.
>>
>> I was looking at SpaceTally and I found that maybe a better implementation
>> could be something like this:
>>
>> Object >> sizeInMemory
>>    "Answer the number of bytes consumed by this instance including object
>> header."
>>
>>    | isCompact instVarBytes bytesPerElement headerBytes total contentBytes
>> |
>>    isCompact := self class indexIfCompact > 0.
>>    instVarBytes := self class instSize * 4.
>>    self class isVariable
>>        ifTrue: [
>>            bytesPerElement := self class isBytes ifTrue: [1] ifFalse: [4].
>>            total := 0.
>>            contentBytes := instVarBytes + (self basicSize *
>> bytesPerElement).
>>                headerBytes :=
>>                    contentBytes > 255
>>                        ifTrue: [12]
>>                        ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].
>>                total :=  headerBytes + contentBytes.
>>            ^ total]
>>        ifFalse: [
>>            headerBytes :=
>>                instVarBytes > 255
>>                    ifTrue: [12]
>>                    ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].
>>            ^ headerBytes + instVarBytes ].
>>
>>
>>
>> I guess I did some mistake but if we can arrive to a good implementation it
>> would be really cool.
>>
>> Thanks
>>
>> mariano
>>
>>
>> Please, at least do some refactoring :)
>>
>> Object >> sizeInMemory
>>    "Answer the number of bytes consumed by this instance including object
>> header."
>>    | isCompact headerBytes contentBytes |
>>
>>    isCompact := self class indexIfCompact > 0.
>>    contentBytes := self class instSize * Smalltalk wordSize. "inst vars"
>>
>>    self class isVariable ifTrue:
>>        [ |bytesPerElement|
>>            bytesPerElement := self class isBytes ifTrue: [1] ifFalse: [4].
>>            contentBytes := contentBytes + (self basicSize *
>> bytesPerElement)].
>>
>>      headerBytes :=
>>                    contentBytes > 255
>>                        ifTrue: [12]
>>                        ifFalse: [isCompact ifTrue: [4] ifFalse: [8]].
>>            ^ headerBytes + instVarBytes
>>
>> Also, in a 64-bit image, I suspect you may have to make a distinction
>> between class isWords as well.
>> ie:
>> self class isBytes ifTrue: [1] ifFalse: [self class isWords ifTrue: [4]
>> ifFalse: [Smalltalk wordSize]]
>>
>> Cheers,
>> Henry
>>
>> _______________________________________________
>> Pharo-project mailing list
>> [hidden email]
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
>>
> _______________________________________________
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