Hands-On High Performance with Go

The P struct

This struct is labeled P for processor. The P struct represents a logical processor. This is set by GOMAXPROCS (which should be equivalent to the number of cores available after Go version 1.5). P maintains a queue of all of the goroutines (defined by the G struct). When you invoke a new goroutine using the Go executor, this new goroutine gets inserted into P's queue. If P doesn't have an associated M struct, it will allocate a new M. Some notable P struct parameters are the following:

• The P struct ID (id)
• A back link to an associated M struct if applicable (m)
• A pool of available defer structs (deferpool)
• The queue of runnable goroutines (runq)
• A struct of available Gs (gFree)