ceremonyclient/utils/runtime/runtime.go

package runtime

import (
	"log"
	"runtime"
)

const minimumCores = 3

// WorkerCount returns the number of workers to use CPU bound tasks.
// It will use GOMAXPROCS as a base, and then subtract a number of CPUs
// which are meant to be left for other tasks, such as networking.
func WorkerCount(requested int, validate bool, legacy bool) int {
	n := runtime.GOMAXPROCS(0)
	if validate {
		if n < minimumCores {
			log.Panic("invalid system configuration, must have at least 3 cores")
		}
		if requested > 0 && requested < minimumCores {
			log.Panic("invalid worker count, must have at least 3 workers")
		}
	}
	if requested > 0 {
		return min(requested, n)
	}

	if legacy {
		switch {
		case n == 1:
			return 1
		case n <= 4:
			return n - 1
		case n <= 16:
			return n - 2
		case n <= 32:
			return n - 3
		case n <= 64:
			return n - 4
		default:
			return n - 5
		}
	}

	if n == 1 {
		return 1
	}

	return n - 1
}