63 lines
1.3 KiB
Go
63 lines
1.3 KiB
Go
package internal
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import (
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"fmt"
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"os"
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"strings"
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"sync"
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)
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var sysCPU struct {
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once sync.Once
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err error
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num int
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}
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// PossibleCPUs returns the max number of CPUs a system may possibly have
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// Logical CPU numbers must be of the form 0-n
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func PossibleCPUs() (int, error) {
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sysCPU.once.Do(func() {
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sysCPU.num, sysCPU.err = parseCPUsFromFile("/sys/devices/system/cpu/possible")
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})
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return sysCPU.num, sysCPU.err
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}
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func parseCPUsFromFile(path string) (int, error) {
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spec, err := os.ReadFile(path)
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if err != nil {
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return 0, err
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}
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n, err := parseCPUs(string(spec))
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if err != nil {
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return 0, fmt.Errorf("can't parse %s: %v", path, err)
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}
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return n, nil
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}
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// parseCPUs parses the number of cpus from a string produced
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// by bitmap_list_string() in the Linux kernel.
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// Multiple ranges are rejected, since they can't be unified
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// into a single number.
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// This is the format of /sys/devices/system/cpu/possible, it
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// is not suitable for /sys/devices/system/cpu/online, etc.
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func parseCPUs(spec string) (int, error) {
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if strings.Trim(spec, "\n") == "0" {
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return 1, nil
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}
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var low, high int
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n, err := fmt.Sscanf(spec, "%d-%d\n", &low, &high)
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if n != 2 || err != nil {
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return 0, fmt.Errorf("invalid format: %s", spec)
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}
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if low != 0 {
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return 0, fmt.Errorf("CPU spec doesn't start at zero: %s", spec)
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}
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// cpus is 0 indexed
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return high + 1, nil
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}
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