1 files changed, 302 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprog/gc.go b/src/runtime/testdata/testprog/gc.go
new file mode 100644
index 0000000..74732cd
--- /dev/null
+++ b/src/runtime/testdata/testprog/gc.go
@@ -0,0 +1,302 @@
+// Copyright 2015 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"
+	"runtime/debug"
+	"sync/atomic"
+	"time"
+	"unsafe"
+)
+
+func init() {
+	register("GCFairness", GCFairness)
+	register("GCFairness2", GCFairness2)
+	register("GCSys", GCSys)
+	register("GCPhys", GCPhys)
+	register("DeferLiveness", DeferLiveness)
+	register("GCZombie", GCZombie)
+}
+
+func GCSys() {
+	runtime.GOMAXPROCS(1)
+	memstats := new(runtime.MemStats)
+	runtime.GC()
+	runtime.ReadMemStats(memstats)
+	sys := memstats.Sys
+
+	runtime.MemProfileRate = 0 // disable profiler
+
+	itercount := 100000
+	for i := 0; i < itercount; i++ {
+		workthegc()
+	}
+
+	// Should only be using a few MB.
+	// We allocated 100 MB or (if not short) 1 GB.
+	runtime.ReadMemStats(memstats)
+	if sys > memstats.Sys {
+		sys = 0
+	} else {
+		sys = memstats.Sys - sys
+	}
+	if sys > 16<<20 {
+		fmt.Printf("using too much memory: %d bytes\n", sys)
+		return
+	}
+	fmt.Printf("OK\n")
+}
+
+var sink []byte
+
+func workthegc() []byte {
+	sink = make([]byte, 1029)
+	return sink
+}
+
+func GCFairness() {
+	runtime.GOMAXPROCS(1)
+	f, err := os.Open("/dev/null")
+	if os.IsNotExist(err) {
+		// This test tests what it is intended to test only if writes are fast.
+		// If there is no /dev/null, we just don't execute the test.
+		fmt.Println("OK")
+		return
+	}
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	for i := 0; i < 2; i++ {
+		go func() {
+			for {
+				f.Write([]byte("."))
+			}
+		}()
+	}
+	time.Sleep(10 * time.Millisecond)
+	fmt.Println("OK")
+}
+
+func GCFairness2() {
+	// Make sure user code can't exploit the GC's high priority
+	// scheduling to make scheduling of user code unfair. See
+	// issue #15706.
+	runtime.GOMAXPROCS(1)
+	debug.SetGCPercent(1)
+	var count [3]int64
+	var sink [3]interface{}
+	for i := range count {
+		go func(i int) {
+			for {
+				sink[i] = make([]byte, 1024)
+				atomic.AddInt64(&count[i], 1)
+			}
+		}(i)
+	}
+	// Note: If the unfairness is really bad, it may not even get
+	// past the sleep.
+	//
+	// If the scheduling rules change, this may not be enough time
+	// to let all goroutines run, but for now we cycle through
+	// them rapidly.
+	//
+	// OpenBSD's scheduler makes every usleep() take at least
+	// 20ms, so we need a long time to ensure all goroutines have
+	// run. If they haven't run after 30ms, give it another 1000ms
+	// and check again.
+	time.Sleep(30 * time.Millisecond)
+	var fail bool
+	for i := range count {
+		if atomic.LoadInt64(&count[i]) == 0 {
+			fail = true
+		}
+	}
+	if fail {
+		time.Sleep(1 * time.Second)
+		for i := range count {
+			if atomic.LoadInt64(&count[i]) == 0 {
+				fmt.Printf("goroutine %d did not run\n", i)
+				return
+			}
+		}
+	}
+	fmt.Println("OK")
+}
+
+func GCPhys() {
+	// This test ensures that heap-growth scavenging is working as intended.
+	//
+	// It sets up a specific scenario: it allocates two pairs of objects whose
+	// sizes sum to size. One object in each pair is "small" (though must be
+	// large enough to be considered a large object by the runtime) and one is
+	// large. The small objects are kept while the large objects are freed,
+	// creating two large unscavenged holes in the heap. The heap goal should
+	// also be small as a result (so size must be at least as large as the
+	// minimum heap size). We then allocate one large object, bigger than both
+	// pairs of objects combined. This allocation, because it will tip
+	// HeapSys-HeapReleased well above the heap goal, should trigger heap-growth
+	// scavenging and scavenge most, if not all, of the large holes we created
+	// earlier.
+	const (
+		// Size must be also large enough to be considered a large
+		// object (not in any size-segregated span).
+		size    = 4 << 20
+		split   = 64 << 10
+		objects = 2
+
+		// The page cache could hide 64 8-KiB pages from the scavenger today.
+		maxPageCache = (8 << 10) * 64
+
+		// Reduce GOMAXPROCS down to 4 if it's greater. We need to bound the amount
+		// of memory held in the page cache because the scavenger can't reach it.
+		// The page cache will hold at most maxPageCache of memory per-P, so this
+		// bounds the amount of memory hidden from the scavenger to 4*maxPageCache
+		// at most.
+		maxProcs = 4
+	)
+	// Set GOGC so that this test operates under consistent assumptions.
+	debug.SetGCPercent(100)
+	procs := runtime.GOMAXPROCS(-1)
+	if procs > maxProcs {
+		defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(maxProcs))
+		procs = runtime.GOMAXPROCS(-1)
+	}
+	// Save objects which we want to survive, and condemn objects which we don't.
+	// Note that we condemn objects in this way and release them all at once in
+	// order to avoid having the GC start freeing up these objects while the loop
+	// is still running and filling in the holes we intend to make.
+	saved := make([][]byte, 0, objects+1)
+	condemned := make([][]byte, 0, objects)
+	for i := 0; i < 2*objects; i++ {
+		if i%2 == 0 {
+			saved = append(saved, make([]byte, split))
+		} else {
+			condemned = append(condemned, make([]byte, size-split))
+		}
+	}
+	condemned = nil
+	// Clean up the heap. This will free up every other object created above
+	// (i.e. everything in condemned) creating holes in the heap.
+	// Also, if the condemned objects are still being swept, its possible that
+	// the scavenging that happens as a result of the next allocation won't see
+	// the holes at all. We call runtime.GC() twice here so that when we allocate
+	// our large object there's no race with sweeping.
+	runtime.GC()
+	runtime.GC()
+	// Perform one big allocation which should also scavenge any holes.
+	//
+	// The heap goal will rise after this object is allocated, so it's very
+	// important that we try to do all the scavenging in a single allocation
+	// that exceeds the heap goal. Otherwise the rising heap goal could foil our
+	// test.
+	saved = append(saved, make([]byte, objects*size))
+	// Clean up the heap again just to put it in a known state.
+	runtime.GC()
+	// heapBacked is an estimate of the amount of physical memory used by
+	// this test. HeapSys is an estimate of the size of the mapped virtual
+	// address space (which may or may not be backed by physical pages)
+	// whereas HeapReleased is an estimate of the amount of bytes returned
+	// to the OS. Their difference then roughly corresponds to the amount
+	// of virtual address space that is backed by physical pages.
+	var stats runtime.MemStats
+	runtime.ReadMemStats(&stats)
+	heapBacked := stats.HeapSys - stats.HeapReleased
+	// If heapBacked does not exceed the heap goal by more than retainExtraPercent
+	// then the scavenger is working as expected; the newly-created holes have been
+	// scavenged immediately as part of the allocations which cannot fit in the holes.
+	//
+	// Since the runtime should scavenge the entirety of the remaining holes,
+	// theoretically there should be no more free and unscavenged memory. However due
+	// to other allocations that happen during this test we may still see some physical
+	// memory over-use.
+	overuse := (float64(heapBacked) - float64(stats.HeapAlloc)) / float64(stats.HeapAlloc)
+	// Compute the threshold.
+	//
+	// In theory, this threshold should just be zero, but that's not possible in practice.
+	// Firstly, the runtime's page cache can hide up to maxPageCache of free memory from the
+	// scavenger per P. To account for this, we increase the threshold by the ratio between the
+	// total amount the runtime could hide from the scavenger to the amount of memory we expect
+	// to be able to scavenge here, which is (size-split)*objects. This computation is the crux
+	// GOMAXPROCS above; if GOMAXPROCS is too high the threshold just becomes 100%+ since the
+	// amount of memory being allocated is fixed. Then we add 5% to account for noise, such as
+	// other allocations this test may have performed that we don't explicitly account for The
+	// baseline threshold here is around 11% for GOMAXPROCS=1, capping out at around 30% for
+	// GOMAXPROCS=4.
+	threshold := 0.05 + float64(procs)*maxPageCache/float64((size-split)*objects)
+	if overuse <= threshold {
+		fmt.Println("OK")
+		return
+	}
+	// Physical memory utilization exceeds the threshold, so heap-growth scavenging
+	// did not operate as expected.
+	//
+	// In the context of this test, this indicates a large amount of
+	// fragmentation with physical pages that are otherwise unused but not
+	// returned to the OS.
+	fmt.Printf("exceeded physical memory overuse threshold of %3.2f%%: %3.2f%%\n"+
+		"(alloc: %d, goal: %d, sys: %d, rel: %d, objs: %d)\n", threshold*100, overuse*100,
+		stats.HeapAlloc, stats.NextGC, stats.HeapSys, stats.HeapReleased, len(saved))
+	runtime.KeepAlive(saved)
+}
+
+// Test that defer closure is correctly scanned when the stack is scanned.
+func DeferLiveness() {
+	var x [10]int
+	escape(&x)
+	fn := func() {
+		if x[0] != 42 {
+			panic("FAIL")
+		}
+	}
+	defer fn()
+
+	x[0] = 42
+	runtime.GC()
+	runtime.GC()
+	runtime.GC()
+}
+
+//go:noinline
+func escape(x interface{}) { sink2 = x; sink2 = nil }
+
+var sink2 interface{}
+
+// Test zombie object detection and reporting.
+func GCZombie() {
+	// Allocate several objects of unusual size (so free slots are
+	// unlikely to all be re-allocated by the runtime).
+	const size = 190
+	const count = 8192 / size
+	keep := make([]*byte, 0, (count+1)/2)
+	free := make([]uintptr, 0, (count+1)/2)
+	zombies := make([]*byte, 0, len(free))
+	for i := 0; i < count; i++ {
+		obj := make([]byte, size)
+		p := &obj[0]
+		if i%2 == 0 {
+			keep = append(keep, p)
+		} else {
+			free = append(free, uintptr(unsafe.Pointer(p)))
+		}
+	}
+
+	// Free the unreferenced objects.
+	runtime.GC()
+
+	// Bring the free objects back to life.
+	for _, p := range free {
+		zombies = append(zombies, (*byte)(unsafe.Pointer(p)))
+	}
+
+	// GC should detect the zombie objects.
+	runtime.GC()
+	println("failed")
+	runtime.KeepAlive(keep)
+	runtime.KeepAlive(zombies)
+}