runtime: add physical memory scavenging test

This change introduces a test to malloc_test which checks for overuse
of physical memory in the large object treap. Due to fragmentation,
there may be many pages of physical memory that are sitting unused in
large-object space.

For #14045.

Change-Id: I3722468f45063b11246dde6301c7ad02ae34be55
Reviewed-on: https://go-review.googlesource.com/c/138918
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/runtime/malloc_test.go b/src/runtime/malloc_test.go
index e6afc25ea9..f25bfa48af 100644
--- a/src/runtime/malloc_test.go
+++ b/src/runtime/malloc_test.go
@@ -168,6 +168,14 @@ func TestTinyAlloc(t *testing.T) {
 	}
 }
 
+func TestPhysicalMemoryUtilization(t *testing.T) {
+	got := runTestProg(t, "testprog", "GCPhys")
+	want := "OK\n"
+	if got != want {
+		t.Fatalf("expected %q, but got %q", want, got)
+	}
+}
+
 type acLink struct {
 	x [1 << 20]byte
 }