how to get Heap size of a program

Question

How to find heap memory size of a c++ program under linux platform ?I need heap memory space before the usage of new or malloc and also after that.can anyone help?

#include <malloc.h>
#include <iostream>
int main()
{

     //here need heap memory space
     unsigned char* I2C_Read_Data= new unsigned char[250];
     //get heap memory space After the usage of new 
     return 0;
 }

@UmNyobe: That's odd, since usually `new` calls `::operator new()`, which in turn is usually implemented via `malloc()`... — Kerrek SB, Mar 17 '12 at 09:45
http://stackoverflow.com/questions/1350819/c-free-store-vs-heap — UmNyobe, Mar 17 '12 at 09:48
let me correct this : new and malloc don't **necessarily** use the same region... — UmNyobe, Mar 17 '12 at 09:49
I don't know,but I hear that the free store and heap can be used interchangeably .Anyway can you please suggest a function for finding dynamic memory space of a c program before and after the allocation and de_allocation? — Anu, Mar 19 '12 at 04:40

score 6 · Answer 1 · answered Mar 17 '12 at 15:20

You can also add heap tracking to your own programs by overloading the new and delete operators. In a game engine I am working on, I have all memory allocation going through special functions, which attach each allocation to a particular heap tracker object. This way, at any given moment, I can pull up a report and see how much memory is being taken up by entities, actors, Lua scripts, etc.

It's not as thorough as using an external profiler (particularly when outside libraries handle their own memory management), but it is very nice for seeing exactly what memory you were responsible for.

sample of my memory tables

score 5 · Answer 2 · answered Mar 17 '12 at 09:41

5

Use valgrind's heap profiler: Massif

answered Mar 17 '12 at 09:41

eyalm

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1

I am using 'arm-linux' platform....How valgrind's can be used with this platform?any idea? – Anu Mar 19 '12 at 06:56

score 2 · Answer 3 · edited May 23 '17 at 12:34

On Linux you can read /proc/[pid]/statm to get memory usage information.

Provides information about memory usage, measured in pages. The columns are:

              size       total program size
                         (same as VmSize in /proc/[pid]/status)
              resident   resident set size
                         (same as VmRSS in /proc/[pid]/status)
              share      shared pages (from shared mappings)
              text       text (code)
              lib        library (unused in Linux 2.6)
              data       data + stack
              dt         dirty pages (unused in Linux 2.6)

See the man page for more details.

Answer by Adam Zalcman to this question describes some interesting details of the heap allocation

The units are pages. You can use getconf PAGE_SIZE to know how big a page is in bytes. — Sergio Martins, May 05 '17 at 15:06

score 1 · Answer 4 · answered Mar 17 '12 at 09:31

1

You can use the getrlimit function call and pass the RLIMIT_DATA for the resource. That should give you the size of the data segment for your program.

answered Mar 17 '12 at 09:31

Gangadhar

1,893
9
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Thank you for the reply ,can you please give me a sample code ? – Anu Mar 17 '12 at 10:00
A simple search would have yielded links like this - http://www.linuxquestions.org/questions/programming-9/getrlimit-is-setting-soft-and-hard-limits-to-1-why-160165/ – Gangadhar Mar 17 '12 at 10:07
Hi, In this it shows the memory space,but not changed after space is allocated. – Anu Mar 19 '12 at 04:03
getrlimit returns the limit for heap, not what is currently used – nmgeek Jan 05 '19 at 22:01

score 0 · Answer 5 · answered Mar 26 '15 at 19:01

0

You can try "mallinfo" and "malloc_info". They might work. mallinfo has issues when you allocate more than 2GB. malloc_info is o/s specific and notably very weird. I agree - very often it's nice to do this stuff without 3rd party tools.

answered Mar 26 '15 at 19:01

Erik Aronesty

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score 0 · Answer 6 · answered Mar 17 '12 at 15:24

Apart from external inspection, you can also instrument your implementation of malloc to let you inspect those statistics. jemalloc and tcmalloc are implementations that, on top of performing better for multithreaded code that typical libc implementations, add some utility functions of that sort.

To dig deeper, you should learn a bit more how heap allocation works. Ultimately, the OS is the one assigning memory to processes as they ask for it, however requests to the OS (syscalls) are slower than regular calls, so in general an implementation of malloc will request large chunks to the OS (4KB or 8KB blocks are common) and the subdivise them to serve them to its callers.

You need to identify whether you are interested in the total memory consumed by the process (which includes the code itself), the memory the process requested from the OS within a particular procedure call, the memory actually in use by the malloc implementation (which adds its own book-keeping overhead, however small) or the memory you requested.

Also, fragmentation can be a pain for the latter two, and may somewhat blurs the differences between really used and assigned to.

how to get Heap size of a program

6 Answers6

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