英文:
How can I see where runtime.futex is coming from? It only has "System" as parent
问题
使用go tool pprof运行带有https://github.com/vimeo/statsdaemon的CPU分析文件，并输入“web”，我得到了一个包含大量“runtime.futex”的SVG分析文件。但是我看不出它是从哪里来的，它只是显示为“System”。
我想知道我的程序调用了哪些代码，导致了这么多时间花在了runtime.futex上。
为了确保，我传递了'-nodefraction=0'，这样它就不会在web svg视图中删除节点，尽管它显示“showing top 80 nodes out of 246 (cum >= 0.11s)”，也许这与此有关。
我尝试了https://code.google.com/p/gperftools/，结果显示相同。
可视化工具没有删除任何节点或边，但是“runtime.futex”仍然显示在“System”下面，这是根节点吗？
英文:
Running go tool pprof with a cpu profile for https://github.com/vimeo/statsdaemon and typing "web" I get an svg profile with extensive use of "runtime.futex". But I can't see where it's coming from, it just says "System".
I want to know which code my program invokes, that causes so much time spent in runtime.futex.
To be sure I passed '-nodefraction=0' which makes it not drop nodes in the web svg view, though it says "showing top 80 nodes out of 246 (cum >= 0.11s)", maybe this is related.
I tried https://code.google.com/p/gperftools/ and it shows the same.
The viz drops no nodes or edges, but still "runtime.futex" just shows up under "System" and that's the root node?
答案1
得分: 8
一个futex或者叫做"快速用户空间互斥锁"，是Linux系统调用，用于基本的锁定。我想Go运行时在内部会经常使用它。
没有看到代码的情况下很难确定，但对于具有大量协调和使用通道的高并发代码，可能确实是来自System的futex调用，而不是特定的函数。
英文:
A futex or "Fast user space mutex" is a linux system call that is used for basic locking. I imagine the go runtime uses it quite a bit under the hood.
Without seeing some of the code it's hard to say for sure but for highly concurrent code with a lot of coordination using channels it's possible that the futex calls really are coming from System and no particular function.
答案2
得分: 5
当我遇到这样的问题时，我使用了runtime/trace，在其中我看到某个函数被频繁调用，而这个函数通过以下方式创建了一个新的ticker：
ticker := time.NewTicker()
但是没有通过以下方式停止它：
defer ticker.Stop()
此外，不要忘记停止定时器：
timer := time.NewTimer(duration)
defer timer.Stop()
英文:
When I've faced with such issue I've used runtime/trace where I've see that some function was called very often and this function creates new ticker by
ticker := time.NewTicker()
but does not stop it by
defer ticker.Stop()
Also, don't forget to stop timers as well:
timer := time.NewTimer(duration)
defer timer.Stop()
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