【高级技巧】分位数统计：延迟的p95与p99口径

local BOUNDS = { 50, 100, 200, 500, 1000, 2000 }
local counts = {}
local function record(ms)
    local b = 1
    while b <= #BOUNDS and ms > BOUNDS[b] do
        b = b + 1
    end
    counts[b] = (counts[b] or 0) + 1
end
local function percentile(p)
    local total = 0
    for i = 1, #BOUNDS + 1 do
        total = total + (counts[i] or 0)
    end
    local target = math.floor(total * p)
    local acc = 0
    for i = 1, #BOUNDS + 1 do
        acc = acc + (counts[i] or 0)
        if acc >= target then
            if i == 1 then
                return BOUNDS[1]
            end
            return BOUNDS[i - 1]
        end
    end
    return 0
end

record(120)
record(80)
record(310)
print("烈火剑法 p95 ≈ " .. percentile(0.95) .. " 毫秒")