Fast(est) way to write a seqence of integer to global memory?

Question

The task is very simple, writting a seqence of integer variable to memory:

Original code:

for (size_t i=0; i<1000*1000*1000; ++i)
{
   data[i]=i;
};
<         


        

Answer 1

Is there any reason why you would expect all of data[] to be in powered-up RAM pages?

The DDR3 pre-fetchter will correctly predict most accesses but the frequent x86-64 page boundaries might be an issue. You're writing to virtual memory, so at each page boundary there's a potential mis-prediction of the pre-fetcher. You can greatly reduce this by using large pages (e.g. MEM_LARGE_PAGES on Windows).