• Go uses its own custom ABI and resizeable stacks, so there's some overhead to switching where the "Go context" must be saved and some things locked.
• Go's goroutines are a kind of preemptive green thread where multiple goroutines share the same OS thread. When calling C, the goroutine scheduler must jump through some hoops to ensure that this caller doesn't stall other goroutines on the same thread.
Calling C code from Go used to be slow, but over the last 10 years much of this overhead has been eliminated. In Go 1.21 (which came with major optimizations), a C call was down to about 40ns [1]. There are now some annotations you can use to further help speed up C calls.
• Go uses its own custom ABI and resizeable stacks, so there's some overhead to switching where the "Go context" must be saved and some things locked.
• Go's goroutines are a kind of preemptive green thread where multiple goroutines share the same OS thread. When calling C, the goroutine scheduler must jump through some hoops to ensure that this caller doesn't stall other goroutines on the same thread.
Calling C code from Go used to be slow, but over the last 10 years much of this overhead has been eliminated. In Go 1.21 (which came with major optimizations), a C call was down to about 40ns [1]. There are now some annotations you can use to further help speed up C calls.
[1] https://shane.ai/posts/cgo-performance-in-go1.21/