runtime: only deduct assist credit for arenas during GC

CL 617876 has changed the original behavior. This modification will restore it.

Change-Id: I72cce82ebed362f99da7548035435397c835c99b
GitHub-Last-Rev: 980ef25b43cbae064f9c9cff0b589b2adbc72f1f
GitHub-Pull-Request: golang/go#74705
Reviewed-on: https://go-review.googlesource.com/c/go/+/689436
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <mark@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/runtime/arena.go b/src/runtime/arena.go
index e80799581052a0979f490262f3f3a44a9a0ff401..0aa3876aaa1a74b57f180299537674bc2f3ff15f 100644 (file)
--- a/src/runtime/arena.go
+++ b/src/runtime/arena.go
@@ -745,7 +745,9 @@ func newUserArenaChunk() (unsafe.Pointer, *mspan) {
        // does represent additional work for the GC, but we also have no idea
        // what that looks like until we actually allocate things into the
        // arena).
-       deductAssistCredit(userArenaChunkBytes)
+       if gcBlackenEnabled != 0 {
+               deductAssistCredit(userArenaChunkBytes)
+       }
 
        // Set mp.mallocing to keep from being preempted by GC.
        mp := acquirem()