Understanding glibc malloc trimming

Some program that I am currently working on consumes much more memory than I think it should. So I am trying to understand how glibc malloc trimming works. I wrote the following test: #include <malloc.h> #include <unistd.h> #define NUM_CHUNKS 1000000 #define CHUNCK_SIZE 100 int main() { // disable fast bins mallopt(M_MXFAST, 0); void** array = (void**)malloc(sizeof(void*) * NUM_CHUNKS); // allocat