Go1.14为time.Timer定时器带来巨幅性能提升

先看标准库中的time package benchmark的指标变化:

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Changes in the time package benchmarks:

name old time/op new time/op delta
AfterFunc-12 1.57ms ± 1% 0.07ms ± 1% -95.42% (p=0.000 n=10+8)
After-12 1.63ms ± 3% 0.11ms ± 1% -93.54% (p=0.000 n=9+10)
Stop-12 78.3µs ± 3% 73.6µs ± 3% -6.01% (p=0.000 n=9+10)
SimultaneousAfterFunc-12 138µs ± 1% 111µs ± 1% -19.57% (p=0.000 n=10+9)
StartStop-12 28.7µs ± 1% 31.5µs ± 5% +9.64% (p=0.000 n=10+7)
Reset-12 6.78µs ± 1% 4.24µs ± 7% -37.45% (p=0.000 n=9+10)
Sleep-12 183µs ± 1% 125µs ± 1% -31.67% (p=0.000 n=10+9)
Ticker-12 5.40ms ± 2% 0.03ms ± 1% -99.43% (p=0.000 n=10+10)
Sub-12 114ns ± 1% 113ns ± 3% ~ (p=0.069 n=9+10)
Now-12 37.2ns ± 1% 36.8ns ± 3% ~ (p=0.287 n=8+8)
NowUnixNano-12 38.1ns ± 2% 37.4ns ± 3% -1.87% (p=0.020 n=10+9)
Format-12 252ns ± 2% 195ns ± 3% -22.61% (p=0.000 n=9+10)
FormatNow-12 234ns ± 1% 177ns ± 2% -24.34% (p=0.000 n=10+10)
MarshalJSON-12 320ns ± 2% 250ns ± 0% -21.94% (p=0.000 n=8+8)
MarshalText-12 320ns ± 2% 245ns ± 2% -23.30% (p=0.000 n=9+10)
Parse-12 206ns ± 2% 208ns ± 4% ~ (p=0.084 n=10+10)
ParseDuration-12 89.1ns ± 1% 86.6ns ± 3% -2.78% (p=0.000 n=10+10)
Hour-12 4.43ns ± 2% 4.46ns ± 1% ~ (p=0.324 n=10+8)
Second-12 4.47ns ± 1% 4.40ns ± 3% ~ (p=0.145 n=9+10)
Year-12 14.6ns ± 1% 14.7ns ± 2% ~ (p=0.112 n=9+9)
Day-12 20.1ns ± 3% 20.2ns ± 1% ~ (p=0.404 n=10+9)

数据来源: https://github.com/golang/go/commit/6becb033341602f2df9d7c55cc23e64b925bbee2

从基准测试结果中可以看到,After函数从老版本的1.63ms直接下降到了0.11ms,提升相当恐怖。

我个人对于此次优化的粗浅理解是:

在1.14之前,标准库会在在创建Timer时懒创建goroutinue,全局最多创建64个,这些goroutinue创建好后永远不会退出,每个goroutinue中有一个最小堆,管理着一部分定时器,这些goroutinue会给Go的线程调度模型带来非常大的开销。

而1.14则直接在P上管理Timer,这样调度器在每次调度循环的间隙都可以检查是否有超时的timer需要执行,并且可以通过netpoll进行唤醒,有点类似于epoll的事件驱动模型中的定时器管理。

具体的分析可以看欧长坤大佬对于Go 1.14定时器优化的分析:

本文完,作者yoko,尊重劳动人民成果,转载请注明原文出处: https://pengrl.com/p/20021/

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