[R] About R memory management?

[Peng Yu]

I'm wondering where I can find the detailed descriptions on R memory
management. Understanding this could help me understand the runtime of
R program. For example, depending on how memory is allocated (either
allocate a chuck of memory that is more than necessary for the current
use, or allocate the memory that is just enough for the current use),
the performance of the following program could be very different.
Could somebody let me know some good references?

unsorted_index=NULL
for(i in 1:100) {
  unsorted_index=c(unsorted_index, i)
}
unsorted_index