File size: 3,849 Bytes
e36aeda | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 | // Copyright 2025 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.
package main
import (
"fmt"
"os"
"runtime"
"strconv"
"time"
)
func init() {
register("PrintGOMAXPROCS", PrintGOMAXPROCS)
register("SetLimitThenDefaultGOMAXPROCS", SetLimitThenDefaultGOMAXPROCS)
register("UpdateGOMAXPROCS", UpdateGOMAXPROCS)
register("DontUpdateGOMAXPROCS", DontUpdateGOMAXPROCS)
}
func PrintGOMAXPROCS() {
println(runtime.GOMAXPROCS(0))
}
func mustSetCPUMax(path string, quota int64) {
q := "max"
if quota >= 0 {
q = strconv.FormatInt(quota, 10)
}
buf := fmt.Sprintf("%s 100000", q)
if err := os.WriteFile(path, []byte(buf), 0); err != nil {
panic(fmt.Sprintf("error setting cpu.max: %v", err))
}
}
func mustParseInt64(s string) int64 {
v, err := strconv.ParseInt(s, 10, 64)
if err != nil {
panic(err)
}
return v
}
// Inputs:
// GO_TEST_CPU_MAX_PATH: Path to cgroup v2 cpu.max file.
// GO_TEST_CPU_MAX_QUOTA: CPU quota to set.
func SetLimitThenDefaultGOMAXPROCS() {
path := os.Getenv("GO_TEST_CPU_MAX_PATH")
quota := mustParseInt64(os.Getenv("GO_TEST_CPU_MAX_QUOTA"))
mustSetCPUMax(path, quota)
runtime.SetDefaultGOMAXPROCS()
println(runtime.GOMAXPROCS(0))
}
// Wait for GOMAXPROCS to change from from to to. Times out after 10s.
func waitForMaxProcsChange(from, to int) {
start := time.Now()
for {
if time.Since(start) > 10*time.Second {
panic("no update for >10s")
}
procs := runtime.GOMAXPROCS(0)
println("GOMAXPROCS:", procs)
if procs == to {
return
}
if procs != from {
panic(fmt.Sprintf("GOMAXPROCS change got %d want %d", procs, to))
}
time.Sleep(100*time.Millisecond)
}
}
// Make sure that GOMAXPROCS does not change from curr.
//
// It is impossible to assert that it never changes, so this just makes sure it
// stays for 5s.
func mustNotChangeMaxProcs(curr int) {
start := time.Now()
for {
if time.Since(start) > 5*time.Second {
return
}
procs := runtime.GOMAXPROCS(0)
println("GOMAXPROCS:", procs)
if procs != curr {
panic(fmt.Sprintf("GOMAXPROCS change got %d want %d", procs, curr))
}
time.Sleep(100*time.Millisecond)
}
}
// Inputs:
// GO_TEST_CPU_MAX_PATH: Path to cgroup v2 cpu.max file.
func UpdateGOMAXPROCS() {
// We start with no limit.
ncpu := runtime.NumCPU()
procs := runtime.GOMAXPROCS(0)
println("GOMAXPROCS:", procs)
if procs != ncpu {
panic(fmt.Sprintf("GOMAXPROCS got %d want %d", procs, ncpu))
}
path := os.Getenv("GO_TEST_CPU_MAX_PATH")
// Drop down to 3 CPU.
mustSetCPUMax(path, 300000)
waitForMaxProcsChange(ncpu, 3)
// Drop even further. Now we hit the minimum GOMAXPROCS=2.
mustSetCPUMax(path, 100000)
waitForMaxProcsChange(3, 2)
// Increase back up.
mustSetCPUMax(path, 300000)
waitForMaxProcsChange(2, 3)
// Remove limit entirely.
mustSetCPUMax(path, -1)
waitForMaxProcsChange(3, ncpu)
// Setting GOMAXPROCS explicitly disables updates.
runtime.GOMAXPROCS(3)
mustSetCPUMax(path, 200000)
mustNotChangeMaxProcs(3)
// Re-enable updates. Change is immediately visible.
runtime.SetDefaultGOMAXPROCS()
procs = runtime.GOMAXPROCS(0)
println("GOMAXPROCS:", procs)
if procs != 2 {
panic(fmt.Sprintf("GOMAXPROCS got %d want %d", procs, 2))
}
// Setting GOMAXPROCS to itself also disables updates, despite not
// changing the value itself.
runtime.GOMAXPROCS(runtime.GOMAXPROCS(0))
mustSetCPUMax(path, 300000)
mustNotChangeMaxProcs(2)
println("OK")
}
// Inputs:
// GO_TEST_CPU_MAX_PATH: Path to cgroup v2 cpu.max file.
func DontUpdateGOMAXPROCS() {
// The caller has disabled updates. Make sure they don't happen.
curr := runtime.GOMAXPROCS(0)
println("GOMAXPROCS:", curr)
path := os.Getenv("GO_TEST_CPU_MAX_PATH")
mustSetCPUMax(path, 300000)
mustNotChangeMaxProcs(curr)
println("OK")
}
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