Increase MIN_BUFFER_SIZE to 512 (1024 on 64-bit) This constant decides the smallest (and typical) size of each evbuffer chain. Since this number includes sizeof(evbuffer_chain) overhead, the old value (256) was just too low: on 64-bit platforms, it would spend nearly 20% of the allocations on overhead. The new values mean that we'll be spending closer to 5% of evbuffer allocations on overhead. It would be nice to get this number even lower if we can.