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As mentioned in issue 6715, the buffer growth strategy used by _io.FileIO
has quadratic running time if each reallocation is O(n). The code in
question is new_buffersize() from Modules/_io/fileio.c:
 if (currentsize > SMALLCHUNK) {
 /* Keep doubling until we reach BIGCHUNK;
 then keep adding BIGCHUNK. */
 if (currentsize <= BIGCHUNK)
 return currentsize + currentsize;
 else
 return currentsize + BIGCHUNK;
 }
 return currentsize + SMALLCHUNK;
Is there a reason for this? One possible improvement would be to instead
use the same formula as list.resize() in Objects/listobject.c:
 new_allocated = (newsize >> 3) + (newsize < 9 ? 3 : 6);
which has amortized O(n) running time behaviour.
Your thoughts?