How to measure memory consumption?

This is a discussion on How to measure memory consumption? within the C++ Programming forums, part of the General Programming Boards category; Hi, I have a very complex C++ object (with many class members and some of them are shared between different ...

  1. #1
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    Question How to measure memory consumption?

    Hi, I have a very complex C++ object (with many class members and some of them are shared between different objects).
    What is the best way to measure how much memory this object takes?

    I tried the following:
    before and after creating this object I call
    GetProcessMemoryInfo(hProcess, &pmc, sizeof(pmc))
    and then use difference in pmc.WorkingSetSize between two calls.

    However it doesn't work well since WorkingSetSize increased in balks. So sometimes I get a big memory increase and other times it is zero.

    Is there any system function that allow to measure exactly how much memory was allocated between two calls?

    Thanks in advance for help!

    PS. I develop on Windows using Visual Studio

  2. #2
    Registered User whiteflags's Avatar
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    Create the object and print the result of sizeof.
    Code:
    struct harbl {
       int lol;
    };
    
    cout << sizeof(struct harbl) << endl;
    That's all it takes to do this as every harbl will be this size.

  3. #3
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    I don't think sizeof will not work if I have pointers to dinamically allocated members.

    Lets look at this example:

    Code:
    class A {
       char a[100];
    }
    
    class B {
       char b[100];
    }
    
    static B* GlobalListOfB = new B[10];
    
    
    class C {
        A* myA;
        B* myB;
        C::Init(int i) 
        { 
           myA = new A[1000];
           myB = &GlobalListOfB[i];
        }
    }
    
    main
    {
       C myC;
       
       myC.Init(5);
    
      how to find out what is the size of myC?
      I think sizeof(C) will return just size of two pointers.
    
    }

  4. #4
    Registered User whiteflags's Avatar
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    Well to be completely honest, that doesn't make a difference because the size of C is two pointers. Pointers point to memory that is elsewhere, so if you want the size of one of C's members you have to use sizeof on that member.
    Code:
    sizeof myC->myA / sizeof myC->myA[0];

  5. #5
    (?<!re)tired Mario F.'s Avatar
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    sizeof() will still work with pointers. Despite holding the address of another object, a pointer is still an object. Assuming your pointers take 4 bytes of memory, myC takes 8 bytes.
    Last edited by Mario F.; 06-23-2006 at 03:15 PM.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  6. #6
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    Or you could create your own allocatinghandler. The handler would keep track of how many bytes allocated and stuff like that. You could also have it keep track of memoryleaks and stuff like that. Of course im not sure how that would work with STL (if its even possible to make it work, i doubt it) but its definately good to have your own ruitines for that just for the sole purpose of keeping track of memoryleaks.
    STL Util a small headers-only library with various utility functions. Mainly for fun but feedback is welcome.

  7. #7
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    >> sizeof() will still work with pointers.
    The point is that the OP wants the total amount of memory used by the object, including both the pointers and what they point to, and sizeof won't help with that unless you add a ton of code in a ton of places including other libraries.

    I'm not sure of the right solution myself, but your compiler or a third party program might have tools to help you do this.

  8. #8
    (?<!re)tired Mario F.'s Avatar
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    One possible, albeit ugly way, is to define a vector (because it promises objects will be in sequence) of 2 objects and read the address of each object. Then just do the math.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  9. #9
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    Again, that won't help, since these objects apparently include pointers to other heap allocated memory, and only the pointers will counted in your solution. The OP wants to include the size of all the memory used by the object.

  10. #10
    and the hat of wrongness Salem's Avatar
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    > http://www.devx.com/tips/Tip/5608
    Simply write new/delete for each class and keep a count of how many live instances of each of them you have.
    The rest is simple maths from then on.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  11. #11
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    EDIT: Salem nailed it above, didn't read properly at first. Sorry
    Last edited by jafet; 06-24-2006 at 10:06 AM.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

  12. #12
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    >> Simply write new/delete for each class and keep a count of how many live instances of each of them you have.

    Will that work if your class uses objects from other libraries, like vector or string?

  13. #13
    and the hat of wrongness Salem's Avatar
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    > Will that work if your class uses objects from other libraries, like vector or string?
    Vector for example is declared as
    vector<T, Alloc>
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  14. #14
    Confused Magos's Avatar
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    Code:
    void C::operator delete (void *p){	
      C* pc = static_cast<C*>(p); 
      free(p);	
    }
    Why the cast? Pointless, typo or contains some implicit operation?
    MagosX.com

    Give a man a fish and you feed him for a day.
    Teach a man to fish and you feed him for a lifetime.

  15. #15
    Cat without Hat CornedBee's Avatar
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    No implicit operation there. It's pointless - may be a leftover from some previous code.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
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