runtime: move pacer time updates and state resets into methods

Currently GC pacer updates are applied somewhat haphazardly via direct
field access. To facilitate ease of testing, move these field updates
into methods. Further CLs will move more of these updates into methods.

For #44167.

Change-Id: I25b10d2219ae27b356b5f236d44827546c86578d
Reviewed-on: https://go-review.googlesource.com/c/go/+/309274
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 40 insertions, 1 deletions

diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 980cb2f086..503b8110b3 100644
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -268,13 +268,14 @@ func (c *gcControllerState) init(gcPercent int32) {
 // startCycle resets the GC controller's state and computes estimates
 // for a new GC cycle. The caller must hold worldsema and the world
 // must be stopped.
-func (c *gcControllerState) startCycle() {
+func (c *gcControllerState) startCycle(markStartTime int64) {
 	c.scanWork = 0
 	c.bgScanCredit = 0
 	c.assistTime = 0
 	c.dedicatedMarkTime = 0
 	c.fractionalMarkTime = 0
 	c.idleMarkTime = 0
+	c.markStartTime = markStartTime
 
 	// Ensure that the heap goal is at least a little larger than
 	// the current live heap size. This may not be the case if GC
@@ -441,6 +442,10 @@ func (c *gcControllerState) revise() {
 // userForced indicates whether the current GC cycle was forced
 // by the application.
 func (c *gcControllerState) endCycle(userForced bool) float64 {
+	// Record last heap goal for the scavenger.
+	// We'll be updating the heap goal soon.
+	gcController.lastHeapGoal = gcController.heapGoal
+
 	if userForced {
 		// Forced GC means this cycle didn't start at the
 		// trigger, so where it finished isn't good
@@ -630,6 +635,40 @@ func (c *gcControllerState) findRunnableGCWorker(_p_ *p) *g {
 	return gp
 }
 
+// resetLive sets up the controller state for the next mark phase after the end
+// of the previous one. Must be called after endCycle and before commit, before
+// the world is started.
+//
+// The world must be stopped.
+func (c *gcControllerState) resetLive(bytesMarked uint64) {
+	c.heapMarked = bytesMarked
+	c.heapLive = bytesMarked
+	c.heapScan = uint64(c.scanWork)
+
+	// heapLive was updated, so emit a trace event.
+	if trace.enabled {
+		traceHeapAlloc()
+	}
+}
+
+// logWorkTime updates mark work accounting in the controller by a duration of
+// work in nanoseconds.
+//
+// Safe to execute at any time.
+func (c *gcControllerState) logWorkTime(mode gcMarkWorkerMode, duration int64) {
+	switch mode {
+	case gcMarkWorkerDedicatedMode:
+		atomic.Xaddint64(&c.dedicatedMarkTime, duration)
+		atomic.Xaddint64(&c.dedicatedMarkWorkersNeeded, 1)
+	case gcMarkWorkerFractionalMode:
+		atomic.Xaddint64(&c.fractionalMarkTime, duration)
+	case gcMarkWorkerIdleMode:
+		atomic.Xaddint64(&c.idleMarkTime, duration)
+	default:
+		throw("logWorkTime: unknown mark worker mode")
+	}
+}
+
 // commit sets the trigger ratio and updates everything
 // derived from it: the absolute trigger, the heap goal, mark pacing,
 // and sweep pacing.