What exactly does runtime.Gosched do?

Note: As of Go 1.5, GOMAXPROCS is set to the number of cores of the hardware: golang.org/doc/go1.5#runtime, below the original answer before 1.5. When you run Go program without specifying GOMAXPROCS environment variable, Go goroutines are scheduled for execution in single OS thread. However, to make program appear to be multithreaded (that’s what goroutines are … Read more

How to configure concurrency in .NET Core Web API?

ASP.NET Core application concurrency is handled by its web server. For example: Kestrel var host = new WebHostBuilder() .UseKestrel(options => options.ThreadCount = 8) It is not recommended to set Kestrel thread count to a large value like 1K due to Kestrel async-based implementation. More info: Is Kestrel using a single thread for processing requests like … Read more

What is a memory fence?

For performance gains modern CPUs often execute instructions out of order to make maximum use of the available silicon (including memory read/writes). Because the hardware enforces instructions integrity you never notice this in a single thread of execution. However for multiple threads or environments with volatile memory (memory mapped I/O for example) this can lead … Read more

What is a coroutine?

Coroutines and concurrency are largely orthogonal. Coroutines are a general control structure whereby flow control is cooperatively passed between two different routines without returning. The ‘yield’ statement in Python is a good example. It creates a coroutine. When the ‘yield ‘ is encountered the current state of the function is saved and control is returned … Read more

Would you explain lock ordering?

In the simple case given, unlocking in the reverse order is not necessary to avoid a deadlock. However, as the code gets more complicated, unlocking in the reverse order helps you maintain proper lock ordering. Consider: A.lock(); B.lock(); Foo(); A.unlock(); Bar(); B.unlock(); If Bar() attempts to reacquire A, you’ve effectively broken your lock ordering. You’re … Read more