numcpus

README

numcpus

Package numcpus provides information about the number of CPU.

It gets the number of CPUs (online, offline, present, possible or kernel maximum) on a Linux, Darwin, FreeBSD, NetBSD, OpenBSD, DragonflyBSD or Solaris/Illumos system.

On Linux, the information is retrieved by reading the corresponding CPU topology files in /sys/devices/system/cpu.

Not all functions are supported on Darwin, FreeBSD, NetBSD, OpenBSD, DragonflyBSD and Solaris/Illumos.

Usage

package main

import (
	"fmt"
	"os"

	"github.com/tklauser/numcpus"
)

func main() {
	online, err := numcpus.GetOnline()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetOnline: %v\n", err)
	}
	fmt.Printf("online CPUs: %v\n", online)

	possible, err := numcpus.GetPossible()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetPossible: %v\n", err)
	}
	fmt.Printf("possible CPUs: %v\n", possible)
}

References

• Linux kernel sysfs documenation for CPU attributes
• Linux kernel CPU topology documentation

Documentation

Overview

Package numcpus provides information about the number of CPU.

It gets the number of CPUs (online, offline, present, possible or kernel maximum) on a Linux, Darwin, FreeBSD, NetBSD, OpenBSD or DragonflyBSD system.

On Linux, the information is retrieved by reading the corresponding CPU topology files in /sys/devices/system/cpu.

Not all functions are supported on Darwin, FreeBSD, NetBSD, OpenBSD and DragonflyBSD.

Index

• Variables
• func GetKernelMax() (int, error)
• func GetOffline() (int, error)
• func GetOnline() (int, error)
• func GetPossible() (int, error)
• func GetPresent() (int, error)

Examples

• GetOffline
• GetOnline
• GetPossible
• GetPresent

Variables

var ErrNotSupported = errors.New("function not supported")

ErrNotSupported is the error returned when the function is not supported.

Functions

func GetKernelMax

func GetKernelMax() (int, error)

GetKernelMax returns the maximum number of CPUs allowed by the kernel configuration. This function is only supported on Linux systems.

func GetOffline

func GetOffline() (int, error)

GetOffline returns the number of offline CPUs, i.e. CPUs that are not online because they have been hotplugged off or exceed the limit of CPUs allowed by the kernel configuration (see GetKernelMax). This function is only supported on Linux systems.

Example

package main

import (
	"fmt"
	"os"

	"github.com/tklauser/numcpus"
)

func main() {
	offline, err := numcpus.GetOffline()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetOffline: %v\n", err)
	}
	fmt.Printf("# of offline CPUs: %v\n", offline)
}

func GetOnline

func GetOnline() (int, error)

GetOnline returns the number of CPUs that are online and being scheduled.

Example

package main

import (
	"fmt"
	"os"

	"github.com/tklauser/numcpus"
)

func main() {
	online, err := numcpus.GetOnline()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetOnline: %v\n", err)
	}
	fmt.Printf("# of online CPUs: %v\n", online)
}

func GetPossible

func GetPossible() (int, error)

GetPossible returns the number of possible CPUs, i.e. CPUs that have been allocated resources and can be brought online if they are present.

Example

package main

import (
	"fmt"
	"os"

	"github.com/tklauser/numcpus"
)

func main() {
	possible, err := numcpus.GetPossible()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetPossible: %v\n", err)
	}
	fmt.Printf("# of possible CPUs: %v\n", possible)
}

func GetPresent

func GetPresent() (int, error)

GetPresent returns the number of CPUs present in the system.

Example

package main

import (
	"fmt"
	"os"

	"github.com/tklauser/numcpus"
)

func main() {
	present, err := numcpus.GetPresent()
	if err != nil {
		fmt.Fprintf(os.Stderr, "GetPresent: %v\n", err)
	}
	fmt.Printf("# of present CPUs: %v\n", present)
}