The constant pool starts at source size / 120 entries, 4 at the least,
and doubles at a load of 3/4; each outgrown pair of arrays stays in the
metadata arena. An embedder that interns a fixed set of names into the
pool at every parse (mruby's compiler puts its 58 presyms there, as its
symbol table) grows a short program's pool from 4 to 128 and leaves
about 3 KB behind, as much as the pool itself. With the minimum under
#ifndef it can build with -DPM_CONSTANT_POOL_MIN_CAPACITY=128: measured
on a 32-bit build with 2 KB arena blocks, parsing one REPL line then
holds 6 KB instead of 10 KB. The default stays 4.
https://github.com/ruby/prism/commit/7ed8c71c59
HASUMI Hitoshi
f2f9b55680