Fix FreeBSD total memory.

Like this.
FreeBSD: fix total memory giampaolo/psutil@bd9a58b bd9a58b2af

mem/mem_freebsd.go

@@ -19,7 +19,7 @@ func VirtualMemoryWithContext(ctx context.Context) (*VirtualMemoryStat, error) {
 	if err != nil {
 		return nil, err
 	}
-	pageCount, err := unix.SysctlUint32("vm.stats.vm.v_page_count")
+	physmem, err := unix.SysctlUint64("hw.physmem")
 	if err != nil {
 		return nil, err
 	}
@@ -50,7 +50,7 @@ func VirtualMemoryWithContext(ctx context.Context) (*VirtualMemoryStat, error) {
 
 	p := uint64(pageSize)
 	ret := &VirtualMemoryStat{
-		Total:    uint64(pageCount) * p,
+		Total:    uint64(physmem),
 		Free:     uint64(free) * p,
 		Active:   uint64(active) * p,
 		Inactive: uint64(inactive) * p,

mem/mem_test.go

@@ -32,6 +32,10 @@ func TestVirtual_memory(t *testing.T) {
 		total = v.Used + v.Available
 		totalStr = "used + available"
 	}
+	if runtime.GOOS == "freebsd" {
+		total = v.Used + v.Free + v.Cached + v.Inactive
+		totalStr = "used + free + cached + inactive"
+	}
 	assert.Equal(t, v.Total, total,
 		"Total should be computable (%v): %v", totalStr, v)