LuaJIT + Big Tables + GC

table-gc.lua

#!/usr/bin/luajit-5_1-2.1.0-beta3

local print = print
local collectgarbage = collectgarbage
local pairs = pairs
local tostring = tostring
local module = module

do
	for k in pairs(package) do
		package[k] = nil
	end
	_G = {}
	module("")
end

local gcinfo = function()
	return collectgarbage('count')
end

local function pgc(prefix)
	print(prefix or "", gcinfo())
end

collectgarbage('collect')
pgc("init") --> init	28.09375

local tbl = {}

local i = 1
while i < 10000000 do
	tbl[tostring(i)] = true
	i = i + 1
end

pgc("after while") --> after while	692069.73828125
collectgarbage('collect')
pgc("after 1st collect") --> after 1st collect	692069.41015625
collectgarbage('collect')
pgc("after 2nd collect") --> after 2nd collect	692069.41015625

for key in pairs(tbl) do
	tbl[key] = nil
end

pgc("after 1st for") --> after 1st for	692069.41015625
collectgarbage('collect')
pgc("collect 1") --> collect 1	426011.49609375
collectgarbage('collect')
pgc("collect 2") --> collect 2	401435.49609375

for key in pairs(tbl) do
	print("< ", key)
end

pgc("after 2nd for") --> after 2nd for	401435.49609375

tbl = nil

collectgarbage('collect')
pgc("after 1st collect") --> after 1st collect	2075.46484375
collectgarbage('collect')
pgc("after 2nd collect") --> after 2nd collect	539.46484375