Fraction of access to dynamically allocated memory

Question

I need to find an estimate of what fraction of all memory accesses from an application (written in "C/"C++") goes to dynamically allocated memory (heap/mmap-ed memory regions). Since an estimate should be good enough I was wondering if anybody knows of any sampling technique through hardware performance counters or through tools like Vlagrind/Purify. I really don't want to write my own heavy weight binary instrumentation through tools like PIN. BTW, I am using Linux on x86-64.

Thanks Arka