clone from danieldin95

vendor/golang.org/x/sys/unix/affinity_linux.go

@@ -0,0 +1,124 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// CPU affinity functions
+
+package unix
+
+import (
+	"unsafe"
+)
+
+const cpuSetSize = _CPU_SETSIZE / _NCPUBITS
+
+// CPUSet represents a CPU affinity mask.
+type CPUSet [cpuSetSize]cpuMask
+
+func schedAffinity(trap uintptr, pid int, set *CPUSet) error {
+	_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(*set)), uintptr(unsafe.Pointer(set)))
+	if e != 0 {
+		return errnoErr(e)
+	}
+	return nil
+}
+
+// SchedGetaffinity gets the CPU affinity mask of the thread specified by pid.
+// If pid is 0 the calling thread is used.
+func SchedGetaffinity(pid int, set *CPUSet) error {
+	return schedAffinity(SYS_SCHED_GETAFFINITY, pid, set)
+}
+
+// SchedSetaffinity sets the CPU affinity mask of the thread specified by pid.
+// If pid is 0 the calling thread is used.
+func SchedSetaffinity(pid int, set *CPUSet) error {
+	return schedAffinity(SYS_SCHED_SETAFFINITY, pid, set)
+}
+
+// Zero clears the set s, so that it contains no CPUs.
+func (s *CPUSet) Zero() {
+	for i := range s {
+		s[i] = 0
+	}
+}
+
+func cpuBitsIndex(cpu int) int {
+	return cpu / _NCPUBITS
+}
+
+func cpuBitsMask(cpu int) cpuMask {
+	return cpuMask(1 << (uint(cpu) % _NCPUBITS))
+}
+
+// Set adds cpu to the set s.
+func (s *CPUSet) Set(cpu int) {
+	i := cpuBitsIndex(cpu)
+	if i < len(s) {
+		s[i] |= cpuBitsMask(cpu)
+	}
+}
+
+// Clear removes cpu from the set s.
+func (s *CPUSet) Clear(cpu int) {
+	i := cpuBitsIndex(cpu)
+	if i < len(s) {
+		s[i] &^= cpuBitsMask(cpu)
+	}
+}
+
+// IsSet reports whether cpu is in the set s.
+func (s *CPUSet) IsSet(cpu int) bool {
+	i := cpuBitsIndex(cpu)
+	if i < len(s) {
+		return s[i]&cpuBitsMask(cpu) != 0
+	}
+	return false
+}
+
+// Count returns the number of CPUs in the set s.
+func (s *CPUSet) Count() int {
+	c := 0
+	for _, b := range s {
+		c += onesCount64(uint64(b))
+	}
+	return c
+}
+
+// onesCount64 is a copy of Go 1.9's math/bits.OnesCount64.
+// Once this package can require Go 1.9, we can delete this
+// and update the caller to use bits.OnesCount64.
+func onesCount64(x uint64) int {
+	const m0 = 0x5555555555555555 // 01010101 ...
+	const m1 = 0x3333333333333333 // 00110011 ...
+	const m2 = 0x0f0f0f0f0f0f0f0f // 00001111 ...
+	const m3 = 0x00ff00ff00ff00ff // etc.
+	const m4 = 0x0000ffff0000ffff
+
+	// Implementation: Parallel summing of adjacent bits.
+	// See "Hacker's Delight", Chap. 5: Counting Bits.
+	// The following pattern shows the general approach:
+	//
+	//   x = x>>1&(m0&m) + x&(m0&m)
+	//   x = x>>2&(m1&m) + x&(m1&m)
+	//   x = x>>4&(m2&m) + x&(m2&m)
+	//   x = x>>8&(m3&m) + x&(m3&m)
+	//   x = x>>16&(m4&m) + x&(m4&m)
+	//   x = x>>32&(m5&m) + x&(m5&m)
+	//   return int(x)
+	//
+	// Masking (& operations) can be left away when there's no
+	// danger that a field's sum will carry over into the next
+	// field: Since the result cannot be > 64, 8 bits is enough
+	// and we can ignore the masks for the shifts by 8 and up.
+	// Per "Hacker's Delight", the first line can be simplified
+	// more, but it saves at best one instruction, so we leave
+	// it alone for clarity.
+	const m = 1<<64 - 1
+	x = x>>1&(m0&m) + x&(m0&m)
+	x = x>>2&(m1&m) + x&(m1&m)
+	x = (x>>4 + x) & (m2 & m)
+	x += x >> 8
+	x += x >> 16
+	x += x >> 32
+	return int(x) & (1<<7 - 1)
+}