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| package main | |
| import ( | |
| "fmt" | |
| "runtime" | |
| "sync" | |
| "unsafe" | |
| ) | |
| var stopC = make(chan struct{}) | |
| // stress starts GC repeatedly to enable write barrier. | |
| func stress() { | |
| for { | |
| select { | |
| case <-stopC: | |
| return | |
| default: | |
| runtime.GC() | |
| } | |
| } | |
| } | |
| var wg sync.WaitGroup | |
| var throttle = make(chan struct{}, 1) | |
| //go:noinline | |
| func noPointerArgs(a, b, c, d uint64) { | |
| <-throttle | |
| wg.Done() | |
| } | |
| func main() { | |
| // make large heap to make write barrier longer | |
| x := make(map[string]string) | |
| for i := 0; i < 10000; i++ { | |
| x[fmt.Sprintf("k%v", i)] = fmt.Sprintf("v%v", i) | |
| } | |
| // enable write barrier. | |
| go stress() | |
| // build integer looks like bad pointer. amd64 specific. | |
| y := uint64(uintptr(unsafe.Pointer(&x))) | |
| fmt.Printf("%x -> ", y) | |
| y |= 0x3000000 | |
| fmt.Printf("%x\n", y) | |
| // run go func() | |
| wg.Add(10000000) | |
| for i := 0; i < 10000000; i++ { | |
| throttle <- struct{}{} | |
| go noPointerArgs(y, y, y, y) | |
| } | |
| wg.Wait() | |
| close(stopC) | |
| } |
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