【性能调优】闭包捕获的隐藏成本：upvalue 与内存

---捕获大表 vs 捕获键值的内存对比
local BIG = {}
for i = 1, 100000 do BIG[i] = i end

local function makeByKey()
    local key = "zuma_boss"      -- 捕获小串
    return function() return CONFIG[key] end
end

local function makeByTable()
    return function() return CONFIG["zuma_boss"] end  -- 捕获 CONFIG 引用
end

collectgarbage("collect")
local before = collectgarbage("count")
local fs = {}
for i = 1, 10000 do fs[i] = makeByKey() end
collectgarbage("collect")
print(collectgarbage("count") - before, "KB for 10k closures")

---定时器闭包：到期即解除引用
setontimerex(53, 1)
function Timer.purge()
    for i = #Timer.pending, 1, -1 do
        local t = Timer.pending[i]
        if t.at < os.time() then
            t.fn = nil        -- 解除闭包引用
            t.env = nil       -- 解除捕获的上下文
            table.remove(Timer.pending, i)
        end
    end
end