125 lines
3.2 KiB
Go
125 lines
3.2 KiB
Go
// 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)
|
|
}
|