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Source file src/runtime/debug/garbage_test.go

Documentation: runtime/debug

  // Copyright 2013 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 debug_test
  
  import (
  	"internal/testenv"
  	"runtime"
  	. "runtime/debug"
  	"testing"
  	"time"
  )
  
  func TestReadGCStats(t *testing.T) {
  	defer SetGCPercent(SetGCPercent(-1))
  
  	var stats GCStats
  	var mstats runtime.MemStats
  	var min, max time.Duration
  
  	// First ReadGCStats will allocate, second should not,
  	// especially if we follow up with an explicit garbage collection.
  	stats.PauseQuantiles = make([]time.Duration, 10)
  	ReadGCStats(&stats)
  	runtime.GC()
  
  	// Assume these will return same data: no GC during ReadGCStats.
  	ReadGCStats(&stats)
  	runtime.ReadMemStats(&mstats)
  
  	if stats.NumGC != int64(mstats.NumGC) {
  		t.Errorf("stats.NumGC = %d, but mstats.NumGC = %d", stats.NumGC, mstats.NumGC)
  	}
  	if stats.PauseTotal != time.Duration(mstats.PauseTotalNs) {
  		t.Errorf("stats.PauseTotal = %d, but mstats.PauseTotalNs = %d", stats.PauseTotal, mstats.PauseTotalNs)
  	}
  	if stats.LastGC.UnixNano() != int64(mstats.LastGC) {
  		t.Errorf("stats.LastGC.UnixNano = %d, but mstats.LastGC = %d", stats.LastGC.UnixNano(), mstats.LastGC)
  	}
  	n := int(mstats.NumGC)
  	if n > len(mstats.PauseNs) {
  		n = len(mstats.PauseNs)
  	}
  	if len(stats.Pause) != n {
  		t.Errorf("len(stats.Pause) = %d, want %d", len(stats.Pause), n)
  	} else {
  		off := (int(mstats.NumGC) + len(mstats.PauseNs) - 1) % len(mstats.PauseNs)
  		for i := 0; i < n; i++ {
  			dt := stats.Pause[i]
  			if dt != time.Duration(mstats.PauseNs[off]) {
  				t.Errorf("stats.Pause[%d] = %d, want %d", i, dt, mstats.PauseNs[off])
  			}
  			if max < dt {
  				max = dt
  			}
  			if min > dt || i == 0 {
  				min = dt
  			}
  			off = (off + len(mstats.PauseNs) - 1) % len(mstats.PauseNs)
  		}
  	}
  
  	q := stats.PauseQuantiles
  	nq := len(q)
  	if q[0] != min || q[nq-1] != max {
  		t.Errorf("stats.PauseQuantiles = [%d, ..., %d], want [%d, ..., %d]", q[0], q[nq-1], min, max)
  	}
  
  	for i := 0; i < nq-1; i++ {
  		if q[i] > q[i+1] {
  			t.Errorf("stats.PauseQuantiles[%d]=%d > stats.PauseQuantiles[%d]=%d", i, q[i], i+1, q[i+1])
  		}
  	}
  
  	// compare memory stats with gc stats:
  	if len(stats.PauseEnd) != n {
  		t.Fatalf("len(stats.PauseEnd) = %d, want %d", len(stats.PauseEnd), n)
  	}
  	off := (int(mstats.NumGC) + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
  	for i := 0; i < n; i++ {
  		dt := stats.PauseEnd[i]
  		if dt.UnixNano() != int64(mstats.PauseEnd[off]) {
  			t.Errorf("stats.PauseEnd[%d] = %d, want %d", i, dt.UnixNano(), mstats.PauseEnd[off])
  		}
  		off = (off + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
  	}
  }
  
  var big = make([]byte, 1<<20)
  
  func TestFreeOSMemory(t *testing.T) {
  	var ms1, ms2 runtime.MemStats
  
  	if big == nil {
  		t.Skip("test is not reliable when run multiple times")
  	}
  	big = nil
  	runtime.GC()
  	runtime.ReadMemStats(&ms1)
  	FreeOSMemory()
  	runtime.ReadMemStats(&ms2)
  	if ms1.HeapReleased >= ms2.HeapReleased {
  		t.Errorf("released before=%d; released after=%d; did not go up", ms1.HeapReleased, ms2.HeapReleased)
  	}
  }
  
  var (
  	setGCPercentBallast interface{}
  	setGCPercentSink    interface{}
  )
  
  func TestSetGCPercent(t *testing.T) {
  	testenv.SkipFlaky(t, 20076)
  
  	// Test that the variable is being set and returned correctly.
  	old := SetGCPercent(123)
  	new := SetGCPercent(old)
  	if new != 123 {
  		t.Errorf("SetGCPercent(123); SetGCPercent(x) = %d, want 123", new)
  	}
  
  	// Test that the percentage is implemented correctly.
  	defer func() {
  		SetGCPercent(old)
  		setGCPercentBallast, setGCPercentSink = nil, nil
  	}()
  	SetGCPercent(100)
  	runtime.GC()
  	// Create 100 MB of live heap as a baseline.
  	const baseline = 100 << 20
  	var ms runtime.MemStats
  	runtime.ReadMemStats(&ms)
  	setGCPercentBallast = make([]byte, baseline-ms.Alloc)
  	runtime.GC()
  	runtime.ReadMemStats(&ms)
  	if abs64(baseline-int64(ms.Alloc)) > 10<<20 {
  		t.Fatalf("failed to set up baseline live heap; got %d MB, want %d MB", ms.Alloc>>20, baseline>>20)
  	}
  	// NextGC should be ~200 MB.
  	const thresh = 20 << 20 // TODO: Figure out why this is so noisy on some builders
  	if want := int64(2 * baseline); abs64(want-int64(ms.NextGC)) > thresh {
  		t.Errorf("NextGC = %d MB, want %d±%d MB", ms.NextGC>>20, want>>20, thresh>>20)
  	}
  	// Create some garbage, but not enough to trigger another GC.
  	for i := 0; i < int(1.2*baseline); i += 1 << 10 {
  		setGCPercentSink = make([]byte, 1<<10)
  	}
  	setGCPercentSink = nil
  	// Adjust GOGC to 50. NextGC should be ~150 MB.
  	SetGCPercent(50)
  	runtime.ReadMemStats(&ms)
  	if want := int64(1.5 * baseline); abs64(want-int64(ms.NextGC)) > thresh {
  		t.Errorf("NextGC = %d MB, want %d±%d MB", ms.NextGC>>20, want>>20, thresh>>20)
  	}
  
  	// Trigger a GC and get back to 100 MB live with GOGC=100.
  	SetGCPercent(100)
  	runtime.GC()
  	// Raise live to 120 MB.
  	setGCPercentSink = make([]byte, int(0.2*baseline))
  	// Lower GOGC to 10. This must force a GC.
  	runtime.ReadMemStats(&ms)
  	ngc1 := ms.NumGC
  	SetGCPercent(10)
  	// It may require an allocation to actually force the GC.
  	setGCPercentSink = make([]byte, 1<<20)
  	runtime.ReadMemStats(&ms)
  	ngc2 := ms.NumGC
  	if ngc1 == ngc2 {
  		t.Errorf("expected GC to run but it did not")
  	}
  }
  
  func abs64(a int64) int64 {
  	if a < 0 {
  		return -a
  	}
  	return a
  }
  
  func TestSetMaxThreadsOvf(t *testing.T) {
  	// Verify that a big threads count will not overflow the int32
  	// maxmcount variable, causing a panic (see Issue 16076).
  	//
  	// This can only happen when ints are 64 bits, since on platforms
  	// with 32 bit ints SetMaxThreads (which takes an int parameter)
  	// cannot be given anything that will overflow an int32.
  	//
  	// Call SetMaxThreads with 1<<31, but only on 64 bit systems.
  	nt := SetMaxThreads(1 << (30 + ^uint(0)>>63))
  	SetMaxThreads(nt) // restore previous value
  }
  

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