go - `__GI___pthread_mutex_unlock` takes most of the execution time when using cgo

php editor Zimo found that when using cgo, sometimes you will encounter a problem, that is, `__GI___pthread_mutex_unlock` takes up most of the execution time. This problem may cause performance degradation and affect the running efficiency of the program. In order to solve this problem, we need to deeply understand the function and principle of `__GI___pthread_mutex_unlock` and find the corresponding optimization method. This article will provide a detailed analysis of this problem to help readers better understand and solve this problem.

Question content

I am using cgo to call a c function from go. There is a callback to the go function inside the c function. In other words, I call go -> c -> go.

After running pprof, I noticed that__gi___pthread_mutex_unlocktook up half of the execution time. Afaik, cgo has overhead, especially callbacks from c to go. But strangely, cgo spends half of its execution time doing some locking. Is there something wrong with my code?

main.go

callback.go

Running environment:

lscpu

go language version

This is the pprof result:

Edit: Add running environment

Workaround

Although I can't reproduce it with the above program:

But there is aglobal mutexfor each callback, so if you do parallel callbacks, you'll lose performance.

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