How do goroutines work? (or: goroutines and OS threads relation)

concurrency go goroutine
omribahumi picture omribahumi · Jul 6, 2014 · Viewed 17.2k times · Source

How can other goroutines keep executing whilst invoking a syscall? (when using GOMAXPROCS=1)
As far as I'm aware of, when invoking a syscall the thread gives up control until the syscall returns. How can Go achieve this concurrency without creating a system thread per blocking-on-syscall goroutine?

From the documentation:

Goroutines

They're called goroutines because the existing terms—threads, coroutines, processes, and so on—convey inaccurate connotations. A goroutine has a simple model: it is a function executing concurrently with other goroutines in the same address space. It is lightweight, costing little more than the allocation of stack space. And the stacks start small, so they are cheap, and grow by allocating (and freeing) heap storage as required.

Goroutines are multiplexed onto multiple OS threads so if one should block, such as while waiting for I/O, others continue to run. Their design hides many of the complexities of thread creation and management.

Answer

OneOfOne picture OneOfOne · Jul 6, 2014

If a goroutine is blocking, the runtime will start a new OS thread to handle the other goroutines until the blocking one stops blocking.

Reference : https://groups.google.com/forum/#!topic/golang-nuts/2IdA34yR8gQ

Related questions

Catching return values from goroutines

The below code gives compilation error saying 'unexpected go': x := go doSomething(arg) func doSomething(arg int) int{ ... return my_int_value } I know, I can fetch the return value if call the function normally, without using goroutine. Or I …

Read More
Golang concurrency: how to append to the same slice from different goroutines

I have concurrent goroutines which want to append a (pointer to a) struct to the same slice. How do you write that in Go to make it concurrency-safe? This would be my concurrency-unsafe code, using a wait group: var wg …

Read More
Golang context.WithValue: how to add several key-value pairs

With Go's context package it is possible to pass request-specific data to the stack of request handling functions using func WithValue(parent Context, key, val interface{}) Context This creates a new Context which is a copy of parent and contains …

Read More