Member Avatar for sommanatt

How do I get the memory usage of my c++ program? Which instruction that i can put in my program and it can tell the size of memory that my program used?

Thank you

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Dani AI

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since you are on Ubuntu, the most trustworthy numbers come from the OS: the process’s resident set size (RSS). Counting your own allocations (as suggested) will not reflect allocator overhead, alignment, thread stacks, or what the kernel actually maps. And yes, small allocations can bump usage by a full page, as noted. There is no standard C++ API for this; you need per-OS calls.

Here is a minimal Linux-friendly helper that reports current RSS and peak RSS in bytes. It uses /proc/self/statm for current RSS and getrusage() for the high-water mark. Note the unit differences for ru_maxrss.

#include <sys/resource.h>
#include <unistd.h>
#include <cstdio>
#include <cstddef>

static size_t peak_rss_bytes() {
    rusage ru{};
    if (getrusage(RUSAGE_SELF, &ru) == 0) {
#ifdef __APPLE__
        return (size_t)ru.ru_maxrss;          // bytes on macOS
#else
        return (size_t)ru.ru_maxrss * 1024;   // kilobytes on Linux
#endif
    }
    return 0;
}

static size_t current_rss_bytes() {
#if defined(__linux__)
    long dummy = 0, rss_pages = 0;
    if (FILE* f = std::fopen("/proc/self/statm", "r")) {
        if (std::fscanf(f, "%ld %ld", &dummy, &rss_pages) != 2) rss_pages = 0;
        std::fclose(f);
    }
    return (size_t)rss_pages * (size_t)sysconf(_SC_PAGESIZE);
#else
    return 0; // use your platform's API here
#endif
}

On Linux, ru_maxrss is in kilobytes; on macOS it is bytes. /proc/self/statm reports page counts; multiply by page size for bytes. (man7.org)

For a portable workflow (answering ): there is no OS-independent call in standard C++. Use OS APIs behind #ifdef (e.g., Windows GetProcessMemoryInfo), or profile externally. For detailed heap timelines on Ubuntu, valgrind --tool=massif ./your_app then ms_print massif.out.* gives peak and breakdowns; add --stacks=yes if you also want stack usage. (learn.microsoft.com)

Recommended Answers

All 7 Replies

Member Avatar for hammerhead

One way to go about it would be to add counters for each datatype. Initialize the counters to the number of static declarations of the datatype and increment them by one whenever memory for that datatype is allocated dynamically. In the end you can multiply the counters to the size of respective datatypes to get the memory used by that datatpe.

Add all counters to get the total memory used by the program. For example

int a,b,c,*d;
char x,y;
int total;
int mem_int=6; //for a,b,c,mem_int,mem_char,total
int mem_char=2;
cin>>c;
d=new int[c];
mem_int+=c;

mem_int=mem_int * sizeof(int);
mem_char=mem_char*sizeof(char);

total=mem_int+mem_char;
cout<<total;

There may be better ways of doing it, i am not sure if we have to add the memory of d or not, maybe some of the more experienced members can help out with that.

Member Avatar for Asat232

you can use Win API ::GetProcessMemoryInfo
But the system allocates memory in blocks (i don't remember exactly 4k or so) and after you allocate two bytes for example memory usage may become 4k more

Member Avatar for sommanatt

Thank you everyone!!
I'm sorry forgetting to tell u that i'm running my c++ program on ubuntu.

Member Avatar for Nick Evan

Perhaps a debugger like Valgrind will have an option for this?

Member Avatar for armin651987

wow this getrusage() really helped me. ;)
thank you alot :D

Member Avatar for myle

Is there a OS independent way of getting these statistics?
AFAIK, LEDA can do it, but I need a non proprietary solution.

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