runtime: use 64k page rounding on arm64

Fixes #11886.

Change-Id: I9392fd2ef5951173ae275b3ab42db4f8bd2e1d7a
Reviewed-on: https://go-review.googlesource.com/12747Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/runtime/arch1_arm64.go

@@ -8,7 +8,7 @@ const (
 	thechar        = '7'
 	_BigEndian     = 0
 	_CacheLineSize = 32
-	_PhysPageSize  = 4096*(1-goos_darwin) + 16384*goos_darwin
+	_PhysPageSize  = 65536
 	_PCQuantum     = 4
 	_Int64Align    = 8
 	hugePageSize   = 0

src/runtime/debug/garbage_test.go

@@ -88,7 +88,8 @@ func TestReadGCStats(t *testing.T) {
 var big = make([]byte, 1<<20)
 
 func TestFreeOSMemory(t *testing.T) {
-	if runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOOS == "nacl" || (runtime.GOOS == "darwin" && runtime.GOARCH == "arm64") {
+	if runtime.GOARCH == "arm64" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" ||
+		runtime.GOOS == "nacl" {
 		t.Skip("issue 9993; scavenger temporarily disabled on systems with physical pages larger than logical pages")
 	}
 	var ms1, ms2 runtime.MemStats