英文:
Golang profiling - top10 shows only one line with 100%
问题
我试图对我的Go库进行性能分析，找出为什么比同样的C++代码慢这么多的原因。
我有一个简单的基准测试：
func BenchmarkFile(t *testing.B) {
tmpFile, err := ioutil.TempFile("", TMP_FILE_PREFIX)
fw, err := NewFile(tmpFile.Name())
text := []byte("testing")
for i := 0; i < b.N; i++ {
_, err = fw.Write(text)
}
fw.Close()
}
NewFile函数返回一个自定义的Writer，它将数据编码为我们的二进制表示形式，甚至可以对其进行压缩，并写入文件系统。
运行go test -bench . -memprofile mem.out -cpuprofile cpu.out后，我得到了以下结果：
PASS
BenchmarkFile-16 2000000000 0.20 ns/op
ok .../writer/iowriter 9.074s
然后进行分析：
# go tool pprof cpu.out
Entering interactive mode (type "help" for commands)
(pprof) top10
930ms of 930ms total (100%)
flat flat% sum% cum cum%
930ms 100% 100% 930ms 100%
(pprof)
我甚至尝试编写一个使用我的writer的example.go应用程序，并按照http://blog.golang.org/profiling-go-programs中所示添加了pprof.StartCPUProfile(f)，但结果相同。
我做错了什么，如何确定我的库的瓶颈在哪里？
提前谢谢你的帮助！
英文:
I try to profiling my go library, to find out what is the cause of being so much slower than same thing in c++.
I have simple benchmark
func BenchmarkFile(t *testing.B) {
tmpFile, err := ioutil.TempFile("", TMP_FILE_PREFIX)
fw, err := NewFile(tmpFile.Name())
text := []byte("testing")
for i := 0; i < b.N; i++ {
_, err = fw.Write(text)
}
fw.Close()
}
NewFile return my custom Writer which encodes data to our binary representation, even compress them, and write to file system.
Running go test -bench . -memprofile mem.out -cpuprofile cpu.out I get
PASS
BenchmarkFile-16 2000000000 0.20 ns/op
ok .../writer/iowriter 9.074s
Than analysing it
# go tool pprof cpu.out
Entering interactive mode (type "help" for commands)
(pprof) top10
930ms of 930ms total ( 100%)
flat flat% sum% cum cum%
930ms 100% 100% 930ms 100%
(pprof)
I even try to write example.go app which is using my writer, and add pprof.StartCPUProfile(f) as is shown in http://blog.golang.org/profiling-go-programs but with same result.
What am I doing wrong, and how can I determine what is bottleneck of my lib?
Thank you in advance
答案1
得分: 8
好的，以下是翻译好的内容：
好的，这很简单，我忘记在go工具pprof中添加二进制文件，所以应该是这样的：
# go tool pprof write cpu.out
进入交互模式（输入“help”获取命令列表）
(pprof) top10
总时间 7.38秒中的 7.02秒（占比95.12%）
删除了14个节点（累计时间小于等于0.04秒）
显示32个节点中的前10个（累计时间大于等于0.19秒）
占比 占比% 总占比 累计时间 累计时间%
6.55秒 88.75% 88.75% 6.76秒 91.60% syscall.Syscall
...
在使用基准测试时，也会创建二进制文件，并且使用它会得到相同的结果。
英文:
Ok it's easy, I miss to add binary to go tool pprof, si it has to be
# go tool pprof write cpu.out
Entering interactive mode (type "help" for commands)
(pprof) top10
7.02s of 7.38s total (95.12%)
Dropped 14 nodes (cum <= 0.04s)
Showing top 10 nodes out of 32 (cum >= 0.19s)
flat flat% sum% cum cum%
6.55s 88.75% 88.75% 6.76s 91.60% syscall.Syscall
...
and when using benchmark tests, binary is created there and using it gives same result.
答案2
得分: 1
进一步解释sejvolnd的答案：
pprof 需要将生成 cpu.out 文件的二进制文件作为第一个参数。
因此，你需要将命令运行为 go tool pprof <你的程序的go二进制文件> <生成的性能分析输出文件>。
例如：go tool pprof go_binary cpu.pprof。
英文:
To expand on sejvolnd's answer:
pprof needs the binary that actually generated cpu.out file as a first argument.
So you need to run the command as go tool pprof <go binary of your program> <generaged profiling output file>
e.g. go tool pprof go_binary cpu.pprof
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