We receive values as int64_t, but when we compute the sum, we store it as
int. This doesn't make sense as we eventually cast it to double when
computing the average. We should instead store the sum as int64_t.
This change adds an average function to time how long it takes the GPU
to copy and map the texture, and then uses this average to sleep for 80%
of this average lowering CPU usage and potentially decreasing lock
contention.
