What is the cost of memory access?
- by Jurily
We like to think that a memory access is fast and constant, but on modern architectures/OSes, that's not necessarily true.
Consider the following C code:
int i = 34;
int *p = &i;
// do something that may or may not involve i and p
{...}
// 3 days later:
*p = 643;
What is the estimated cost of this last assignment in CPU instructions, if
i is in L1 cache,
i is in L2 cache,
i is in L3 cache,
i is in RAM proper,
i is paged out to an SSD disk,
i is paged out to a traditional disk?
Where else can i be?
Of course the numbers are not absolute, but I'm only interested in orders of magnitude. I tried searching the webs, but Google did not bless me this time.
