runtime: clarify work.bytesMarked documentation

Change-Id: If5132400aac0ef00e467958beeaab5e64d053d10
Reviewed-on: https://go-review.googlesource.com/c/go/+/619099
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Austin Clements <austin@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index a2b6b979c1500b5fe10b210e8059033097bbeee9..e9cb2fdfc399cf0001d4962989386820fd93a63b 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -334,11 +334,12 @@ type workType struct {
 
        // bytesMarked is the number of bytes marked this cycle. This
        // includes bytes blackened in scanned objects, noscan objects
-       // that go straight to black, and permagrey objects scanned by
-       // markroot during the concurrent scan phase. This is updated
-       // atomically during the cycle. Updates may be batched
-       // arbitrarily, since the value is only read at the end of the
-       // cycle.
+       // that go straight to black, objects allocated as black during
+       // the cycle, and permagrey objects scanned by markroot during
+       // the concurrent scan phase.
+       //
+       // This is updated atomically during the cycle. Updates may be batched
+       // arbitrarily, since the value is only read at the end of the cycle.
        //
        // Because of benign races during marking, this number may not
        // be the exact number of marked bytes, but it should be very