Takahiro Suzuki | d7bf820 | 2020-12-17 20:21:59 +0900 | [diff] [blame] | 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 | } |