Question

我正在golang中编写一个小工具，它读取CSV文件并将每一行传递给一个通道。每行都有一个接收器go-routine。不知怎的，这很慢 - 使用分析我发现程序在runtime.usleep上是68％。我的代码中没有“睡觉”。

有人能指出我可能来自哪里，意味着什么以及如何摆脱它？

(pprof) top10
28.98s of 30.12s total (96.22%)
Dropped 64 nodes (cum <= 0.15s)
Showing top 10 nodes out of 44 (cum >= 19.38s)
  flat  flat%   sum%        cum   cum%
20.53s 68.16% 68.16%     20.53s 68.16%  runtime.usleep
 6.86s 22.78% 90.94%      6.86s 22.78%  syscall.Syscall
 0.30s     1% 91.93%      0.30s     1%  runtime/internal/atomic.Cas64
 0.28s  0.93% 92.86%      0.28s  0.93%  runtime.mach_semaphore_signal
 0.26s  0.86% 93.73%     19.15s 63.58%  runtime.findrunnable
 0.24s   0.8% 94.52%      0.24s   0.8%  runtime.mach_semaphore_wait
 0.21s   0.7% 95.22%     17.11s 56.81%  runtime.runqgrab
 0.13s  0.43% 95.65%      0.23s  0.76%  runtime.runqempty
 0.12s   0.4% 96.05%      4.17s 13.84%  runtime.lock
 0.05s  0.17% 96.22%     19.38s 64.34%  runtime.schedule
(pprof)

相关源代码：

[...snip from main...]
var wg_p sync.WaitGroup
var wg_w sync.WaitGroup

for i := 0; i < workercount; i++ {
    wg_p.Add(1)
    go func(i int) {
        processor(i, chn_read, chn_write)
        wg_p.Done()
    }(i)
}

wg_w.Add(1)
go func() {
    writer(chn_write)
    wg_w.Done()
}()

// read headers/1st line from csv
headers, _ := csvf.Read()
g_fieldnames = headers
chn_write <- g_fieldnames

// read 'n feed linewise
for {
    chunk, _ := csvf.Read()
    if chunk == nil {
        close(chn_read)
        break
    }
    chn_read <- chunk
}
[...snip end from main...]

和go-routines

func processor(num_p int, chn_read chan []string, chn_write chan []string) {
    for msg := range chn_read {
        // snipped working on 'msg'
        chn_write <- msg
    }
}

func writer(chn_write chan []string) {
    fout, _ := os.Create("./out.csv")
    defer fout.Close()
    w := csv.NewWriter(fout)
    counter := 0
    for msg := range chn_write {
        w.Write(msg)
        counter++
    }
    w.Flush()
}

golang profile runtime.usleep在70％

0 个答案: