// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// CPU affinity functions
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package unix
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import (
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"math/bits"
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"unsafe"
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)
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const cpuSetSize = _CPU_SETSIZE / _NCPUBITS
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// CPUSet represents a CPU affinity mask.
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type CPUSet [cpuSetSize]cpuMask
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func schedAffinity(trap uintptr, pid int, set *CPUSet) error {
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_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(*set)), uintptr(unsafe.Pointer(set)))
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if e != 0 {
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return errnoErr(e)
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}
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return nil
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}
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// SchedGetaffinity gets the CPU affinity mask of the thread specified by pid.
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// If pid is 0 the calling thread is used.
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func SchedGetaffinity(pid int, set *CPUSet) error {
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return schedAffinity(SYS_SCHED_GETAFFINITY, pid, set)
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}
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// SchedSetaffinity sets the CPU affinity mask of the thread specified by pid.
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// If pid is 0 the calling thread is used.
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func SchedSetaffinity(pid int, set *CPUSet) error {
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return schedAffinity(SYS_SCHED_SETAFFINITY, pid, set)
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}
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// Zero clears the set s, so that it contains no CPUs.
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func (s *CPUSet) Zero() {
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for i := range s {
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s[i] = 0
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}
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}
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func cpuBitsIndex(cpu int) int {
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return cpu / _NCPUBITS
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}
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func cpuBitsMask(cpu int) cpuMask {
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return cpuMask(1 << (uint(cpu) % _NCPUBITS))
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}
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// Set adds cpu to the set s.
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func (s *CPUSet) Set(cpu int) {
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i := cpuBitsIndex(cpu)
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if i < len(s) {
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s[i] |= cpuBitsMask(cpu)
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}
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}
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// Clear removes cpu from the set s.
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func (s *CPUSet) Clear(cpu int) {
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i := cpuBitsIndex(cpu)
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if i < len(s) {
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s[i] &^= cpuBitsMask(cpu)
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}
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}
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// IsSet reports whether cpu is in the set s.
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func (s *CPUSet) IsSet(cpu int) bool {
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i := cpuBitsIndex(cpu)
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if i < len(s) {
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return s[i]&cpuBitsMask(cpu) != 0
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}
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return false
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}
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// Count returns the number of CPUs in the set s.
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func (s *CPUSet) Count() int {
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c := 0
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for _, b := range s {
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c += bits.OnesCount64(uint64(b))
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}
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return c
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}
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