runtime: add and use runtime/internal/sys.NotInHeap

Updates #46731

Change-Id: Ic2208c8bb639aa1e390be0d62e2bd799ecf20654
Reviewed-on: https://go-review.googlesource.com/c/go/+/421878
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 0219401c83..205c6d44a8 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1330,7 +1330,8 @@ var persistentChunks *notInHeap
 // The returned memory will be zeroed.
 // sysStat must be non-nil.
 //
-// Consider marking persistentalloc'd types go:notinheap.
+// Consider marking persistentalloc'd types not in heap by embedding
+// runtime/internal/sys.NotInHeap.
 func persistentalloc(size, align uintptr, sysStat *sysMemStat) unsafe.Pointer {
 	var p *notInHeap
 	systemstack(func() {
@@ -1471,14 +1472,12 @@ func (l *linearAlloc) alloc(size, align uintptr, sysStat *sysMemStat) unsafe.Poi
 // notInHeap is off-heap memory allocated by a lower-level allocator
 // like sysAlloc or persistentAlloc.
 //
-// In general, it's better to use real types marked as go:notinheap,
-// but this serves as a generic type for situations where that isn't
-// possible (like in the allocators).
+// In general, it's better to use real types which embed
+// runtime/internal/sys.NotInHeap, but this serves as a generic type
+// for situations where that isn't possible (like in the allocators).
 //
 // TODO: Use this as the return type of sysAlloc, persistentAlloc, etc?
-//
-//go:notinheap
-type notInHeap struct{}
+type notInHeap struct{ _ sys.NotInHeap }
 
 func (p *notInHeap) add(bytes uintptr) *notInHeap {
 	return (*notInHeap)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + bytes))