From: Carlos Amedee <carlos@golang.org>
Date: Thu, 2 Jan 2025 19:41:59 +0000 (-0500)
Subject: runtime: set HeapGoal to zero when the GC is disabled
X-Git-Tag: go1.25rc1~30
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=1947c4233a33953088468a23457f6779c34be2d1;p=gostls13.git

runtime: set HeapGoal to zero when the GC is disabled

When the GC is disabled, the tracer should emit a heap goal of 0. Not
setting the heap goal to 0 causes an inaccurate NextGC value to be
emmited.

Fixes #63864

Change-Id: Iecceaca86c0a43c1cc4d9433f1f9bb736f01ccbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/639417
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
---

diff --git a/src/runtime/traceruntime.go b/src/runtime/traceruntime.go
index 98ac1082a8..39adeb4c07 100644
--- a/src/runtime/traceruntime.go
+++ b/src/runtime/traceruntime.go
@@ -574,7 +574,9 @@ func (tl traceLocker) HeapAlloc(live uint64) {
 // HeapGoal reads the current heap goal and emits a HeapGoal event.
 func (tl traceLocker) HeapGoal() {
 	heapGoal := gcController.heapGoal()
-	if heapGoal == ^uint64(0) {
+	// The heapGoal calculations will result in strange numbers if the GC if off. See go.dev/issue/63864.
+	// Check gcPercent before using the heapGoal in the trace.
+	if heapGoal == ^uint64(0) || gcController.gcPercent.Load() < 0 {
 		// Heap-based triggering is disabled.
 		heapGoal = 0
 	}