read_all: Grow buffer exponentially in generic case
In the general case, read_all grows its buffer linearly by just the amount that is currently read from the underlying source. This results in a linear number of reallocs, It might turn out beneficial if the buffer were grown exponentially by multiplying with a constant factor (e.g. 1.5 or 2), thus resulting in only a logarithmic numver of reallocs.
I will provide a patch and benchmarks, but I'm already opening this issue so I won't forget.
See also https://bugs.ruby-lang.org/issues/5353 for more details.