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affinity_linux.go (1927B)

      1 // Copyright 2018 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 // CPU affinity functions
      6 
      7 package unix
      8 
      9 import (
     10 	"math/bits"
     11 	"unsafe"
     12 )
     13 
     14 const cpuSetSize = _CPU_SETSIZE / _NCPUBITS
     15 
     16 // CPUSet represents a CPU affinity mask.
     17 type CPUSet [cpuSetSize]cpuMask
     18 
     19 func schedAffinity(trap uintptr, pid int, set *CPUSet) error {
     20 	_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(*set)), uintptr(unsafe.Pointer(set)))
     21 	if e != 0 {
     22 		return errnoErr(e)
     23 	}
     24 	return nil
     25 }
     26 
     27 // SchedGetaffinity gets the CPU affinity mask of the thread specified by pid.
     28 // If pid is 0 the calling thread is used.
     29 func SchedGetaffinity(pid int, set *CPUSet) error {
     30 	return schedAffinity(SYS_SCHED_GETAFFINITY, pid, set)
     31 }
     32 
     33 // SchedSetaffinity sets the CPU affinity mask of the thread specified by pid.
     34 // If pid is 0 the calling thread is used.
     35 func SchedSetaffinity(pid int, set *CPUSet) error {
     36 	return schedAffinity(SYS_SCHED_SETAFFINITY, pid, set)
     37 }
     38 
     39 // Zero clears the set s, so that it contains no CPUs.
     40 func (s *CPUSet) Zero() {
     41 	for i := range s {
     42 		s[i] = 0
     43 	}
     44 }
     45 
     46 func cpuBitsIndex(cpu int) int {
     47 	return cpu / _NCPUBITS
     48 }
     49 
     50 func cpuBitsMask(cpu int) cpuMask {
     51 	return cpuMask(1 << (uint(cpu) % _NCPUBITS))
     52 }
     53 
     54 // Set adds cpu to the set s.
     55 func (s *CPUSet) Set(cpu int) {
     56 	i := cpuBitsIndex(cpu)
     57 	if i < len(s) {
     58 		s[i] |= cpuBitsMask(cpu)
     59 	}
     60 }
     61 
     62 // Clear removes cpu from the set s.
     63 func (s *CPUSet) Clear(cpu int) {
     64 	i := cpuBitsIndex(cpu)
     65 	if i < len(s) {
     66 		s[i] &^= cpuBitsMask(cpu)
     67 	}
     68 }
     69 
     70 // IsSet reports whether cpu is in the set s.
     71 func (s *CPUSet) IsSet(cpu int) bool {
     72 	i := cpuBitsIndex(cpu)
     73 	if i < len(s) {
     74 		return s[i]&cpuBitsMask(cpu) != 0
     75 	}
     76 	return false
     77 }
     78 
     79 // Count returns the number of CPUs in the set s.
     80 func (s *CPUSet) Count() int {
     81 	c := 0
     82 	for _, b := range s {
     83 		c += bits.OnesCount64(uint64(b))
     84 	}
     85 	return c
     86 }