【高级技巧】内存快照对比：揪出每小时20MB的泄漏

local function snapshot(limit)
    local stat = {}
    local seen = {}
    local function walk(v, tag, depth)
        if depth > 8 or seen[v] then
            return
        end
        if type(v) == "table" then
            seen[v] = true
            stat[tag] = (stat[tag] or 0) + 1
            for k, sub in pairs(v) do
                walk(sub, tag .. "." .. tostring(k), depth + 1)
            end
        end
    end
    for k, v in pairs(_G) do
        walk(v, tostring(k), 1)
    end
    return stat
end
local function diff(s1, s2, topN)
    local rows = {}
    for k, v in pairs(s2) do
        local d = v - (s1[k] or 0)
        if d > 0 then
            rows[#rows + 1] = { tag = k, grow = d }
        end
    end
    table.sort(rows, function(a, b)
        return a.grow > b.grow
    end
    )
    for i = 1, math.min(topN or 10, #rows) do
        print("增长 " .. rows[i].grow .. " 张表：" .. rows[i].tag)
    end
end

local s1 = snapshot()
local s2 = snapshot()
diff(s1, s2, 10)