gc-stress.go

     1  // Copyright 2023 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  // Tests a GC-heavy program. This is useful for shaking out
     6  // all sorts of corner cases about GC-related ranges.
     7  
     8  //go:build ignore
     9  
    10  package main
    11  
    12  import (
    13  	"log"
    14  	"os"
    15  	"runtime"
    16  	"runtime/trace"
    17  	"time"
    18  )
    19  
    20  type node struct {
    21  	children [4]*node
    22  	data     [128]byte
    23  }
    24  
    25  func makeTree(depth int) *node {
    26  	if depth == 0 {
    27  		return new(node)
    28  	}
    29  	return &node{
    30  		children: [4]*node{
    31  			makeTree(depth - 1),
    32  			makeTree(depth - 1),
    33  			makeTree(depth - 1),
    34  			makeTree(depth - 1),
    35  		},
    36  	}
    37  }
    38  
    39  var trees [16]*node
    40  var ballast *[16]*[1024]*node
    41  var sink [][]byte
    42  
    43  func main() {
    44  	for i := range trees {
    45  		trees[i] = makeTree(6)
    46  	}
    47  	ballast = new([16]*[1024]*node)
    48  	for i := range ballast {
    49  		ballast[i] = new([1024]*node)
    50  		for j := range ballast[i] {
    51  			ballast[i][j] = &node{
    52  				data: [128]byte{1, 2, 3, 4},
    53  			}
    54  		}
    55  	}
    56  
    57  	procs := runtime.GOMAXPROCS(-1)
    58  	sink = make([][]byte, procs)
    59  
    60  	for i := 0; i < procs; i++ {
    61  		i := i
    62  		go func() {
    63  			for {
    64  				sink[i] = make([]byte, 4<<10)
    65  			}
    66  		}()
    67  	}
    68  	// Increase the chance that we end up starting and stopping
    69  	// mid-GC by only starting to trace after a few milliseconds.
    70  	time.Sleep(5 * time.Millisecond)
    71  
    72  	// Start tracing.
    73  	if err := trace.Start(os.Stdout); err != nil {
    74  		log.Fatalf("failed to start tracing: %v", err)
    75  	}
    76  	defer trace.Stop()
    77  
    78  	// Let the tracing happen for a bit.
    79  	time.Sleep(400 * time.Millisecond)
    80  }
    81
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