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Source file src/runtime/debug/garbage_test.go

Documentation: runtime/debug

     1  // Copyright 2013 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  package debug_test
     6  
     7  import (
     8  	"internal/testenv"
     9  	"runtime"
    10  	. "runtime/debug"
    11  	"testing"
    12  	"time"
    13  )
    14  
    15  func TestReadGCStats(t *testing.T) {
    16  	defer SetGCPercent(SetGCPercent(-1))
    17  
    18  	var stats GCStats
    19  	var mstats runtime.MemStats
    20  	var min, max time.Duration
    21  
    22  	// First ReadGCStats will allocate, second should not,
    23  	// especially if we follow up with an explicit garbage collection.
    24  	stats.PauseQuantiles = make([]time.Duration, 10)
    25  	ReadGCStats(&stats)
    26  	runtime.GC()
    27  
    28  	// Assume these will return same data: no GC during ReadGCStats.
    29  	ReadGCStats(&stats)
    30  	runtime.ReadMemStats(&mstats)
    31  
    32  	if stats.NumGC != int64(mstats.NumGC) {
    33  		t.Errorf("stats.NumGC = %d, but mstats.NumGC = %d", stats.NumGC, mstats.NumGC)
    34  	}
    35  	if stats.PauseTotal != time.Duration(mstats.PauseTotalNs) {
    36  		t.Errorf("stats.PauseTotal = %d, but mstats.PauseTotalNs = %d", stats.PauseTotal, mstats.PauseTotalNs)
    37  	}
    38  	if stats.LastGC.UnixNano() != int64(mstats.LastGC) {
    39  		t.Errorf("stats.LastGC.UnixNano = %d, but mstats.LastGC = %d", stats.LastGC.UnixNano(), mstats.LastGC)
    40  	}
    41  	n := int(mstats.NumGC)
    42  	if n > len(mstats.PauseNs) {
    43  		n = len(mstats.PauseNs)
    44  	}
    45  	if len(stats.Pause) != n {
    46  		t.Errorf("len(stats.Pause) = %d, want %d", len(stats.Pause), n)
    47  	} else {
    48  		off := (int(mstats.NumGC) + len(mstats.PauseNs) - 1) % len(mstats.PauseNs)
    49  		for i := 0; i < n; i++ {
    50  			dt := stats.Pause[i]
    51  			if dt != time.Duration(mstats.PauseNs[off]) {
    52  				t.Errorf("stats.Pause[%d] = %d, want %d", i, dt, mstats.PauseNs[off])
    53  			}
    54  			if max < dt {
    55  				max = dt
    56  			}
    57  			if min > dt || i == 0 {
    58  				min = dt
    59  			}
    60  			off = (off + len(mstats.PauseNs) - 1) % len(mstats.PauseNs)
    61  		}
    62  	}
    63  
    64  	q := stats.PauseQuantiles
    65  	nq := len(q)
    66  	if q[0] != min || q[nq-1] != max {
    67  		t.Errorf("stats.PauseQuantiles = [%d, ..., %d], want [%d, ..., %d]", q[0], q[nq-1], min, max)
    68  	}
    69  
    70  	for i := 0; i < nq-1; i++ {
    71  		if q[i] > q[i+1] {
    72  			t.Errorf("stats.PauseQuantiles[%d]=%d > stats.PauseQuantiles[%d]=%d", i, q[i], i+1, q[i+1])
    73  		}
    74  	}
    75  
    76  	// compare memory stats with gc stats:
    77  	if len(stats.PauseEnd) != n {
    78  		t.Fatalf("len(stats.PauseEnd) = %d, want %d", len(stats.PauseEnd), n)
    79  	}
    80  	off := (int(mstats.NumGC) + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
    81  	for i := 0; i < n; i++ {
    82  		dt := stats.PauseEnd[i]
    83  		if dt.UnixNano() != int64(mstats.PauseEnd[off]) {
    84  			t.Errorf("stats.PauseEnd[%d] = %d, want %d", i, dt.UnixNano(), mstats.PauseEnd[off])
    85  		}
    86  		off = (off + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
    87  	}
    88  }
    89  
    90  var big = make([]byte, 1<<20)
    91  
    92  func TestFreeOSMemory(t *testing.T) {
    93  	var ms1, ms2 runtime.MemStats
    94  
    95  	if big == nil {
    96  		t.Skip("test is not reliable when run multiple times")
    97  	}
    98  	big = nil
    99  	runtime.GC()
   100  	runtime.ReadMemStats(&ms1)
   101  	FreeOSMemory()
   102  	runtime.ReadMemStats(&ms2)
   103  	if ms1.HeapReleased >= ms2.HeapReleased {
   104  		t.Errorf("released before=%d; released after=%d; did not go up", ms1.HeapReleased, ms2.HeapReleased)
   105  	}
   106  }
   107  
   108  var (
   109  	setGCPercentBallast interface{}
   110  	setGCPercentSink    interface{}
   111  )
   112  
   113  func TestSetGCPercent(t *testing.T) {
   114  	testenv.SkipFlaky(t, 20076)
   115  
   116  	// Test that the variable is being set and returned correctly.
   117  	old := SetGCPercent(123)
   118  	new := SetGCPercent(old)
   119  	if new != 123 {
   120  		t.Errorf("SetGCPercent(123); SetGCPercent(x) = %d, want 123", new)
   121  	}
   122  
   123  	// Test that the percentage is implemented correctly.
   124  	defer func() {
   125  		SetGCPercent(old)
   126  		setGCPercentBallast, setGCPercentSink = nil, nil
   127  	}()
   128  	SetGCPercent(100)
   129  	runtime.GC()
   130  	// Create 100 MB of live heap as a baseline.
   131  	const baseline = 100 << 20
   132  	var ms runtime.MemStats
   133  	runtime.ReadMemStats(&ms)
   134  	setGCPercentBallast = make([]byte, baseline-ms.Alloc)
   135  	runtime.GC()
   136  	runtime.ReadMemStats(&ms)
   137  	if abs64(baseline-int64(ms.Alloc)) > 10<<20 {
   138  		t.Fatalf("failed to set up baseline live heap; got %d MB, want %d MB", ms.Alloc>>20, baseline>>20)
   139  	}
   140  	// NextGC should be ~200 MB.
   141  	const thresh = 20 << 20 // TODO: Figure out why this is so noisy on some builders
   142  	if want := int64(2 * baseline); abs64(want-int64(ms.NextGC)) > thresh {
   143  		t.Errorf("NextGC = %d MB, want %d±%d MB", ms.NextGC>>20, want>>20, thresh>>20)
   144  	}
   145  	// Create some garbage, but not enough to trigger another GC.
   146  	for i := 0; i < int(1.2*baseline); i += 1 << 10 {
   147  		setGCPercentSink = make([]byte, 1<<10)
   148  	}
   149  	setGCPercentSink = nil
   150  	// Adjust GOGC to 50. NextGC should be ~150 MB.
   151  	SetGCPercent(50)
   152  	runtime.ReadMemStats(&ms)
   153  	if want := int64(1.5 * baseline); abs64(want-int64(ms.NextGC)) > thresh {
   154  		t.Errorf("NextGC = %d MB, want %d±%d MB", ms.NextGC>>20, want>>20, thresh>>20)
   155  	}
   156  
   157  	// Trigger a GC and get back to 100 MB live with GOGC=100.
   158  	SetGCPercent(100)
   159  	runtime.GC()
   160  	// Raise live to 120 MB.
   161  	setGCPercentSink = make([]byte, int(0.2*baseline))
   162  	// Lower GOGC to 10. This must force a GC.
   163  	runtime.ReadMemStats(&ms)
   164  	ngc1 := ms.NumGC
   165  	SetGCPercent(10)
   166  	// It may require an allocation to actually force the GC.
   167  	setGCPercentSink = make([]byte, 1<<20)
   168  	runtime.ReadMemStats(&ms)
   169  	ngc2 := ms.NumGC
   170  	if ngc1 == ngc2 {
   171  		t.Errorf("expected GC to run but it did not")
   172  	}
   173  }
   174  
   175  func abs64(a int64) int64 {
   176  	if a < 0 {
   177  		return -a
   178  	}
   179  	return a
   180  }
   181  
   182  func TestSetMaxThreadsOvf(t *testing.T) {
   183  	// Verify that a big threads count will not overflow the int32
   184  	// maxmcount variable, causing a panic (see Issue 16076).
   185  	//
   186  	// This can only happen when ints are 64 bits, since on platforms
   187  	// with 32 bit ints SetMaxThreads (which takes an int parameter)
   188  	// cannot be given anything that will overflow an int32.
   189  	//
   190  	// Call SetMaxThreads with 1<<31, but only on 64 bit systems.
   191  	nt := SetMaxThreads(1 << (30 + ^uint(0)>>63))
   192  	SetMaxThreads(nt) // restore previous value
   193  }
   194  

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