runtime: convert gcController.lastStackScan to atomic type

For #53821.

Change-Id: I6a7dcc9b72683e977a2b8d90e521a53a8a508558
Reviewed-on: https://go-review.googlesource.com/c/go/+/417777
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/align_runtime_test.go b/src/runtime/align_runtime_test.go
index 3f86838ac5af5a05551b58cf8a9081c642832e9e..03309a22d06bfbb113205d3ceec4ec52353f64fa 100644 (file)
--- a/src/runtime/align_runtime_test.go
+++ b/src/runtime/align_runtime_test.go
@@ -28,7 +28,6 @@ var AtomicFields = []uintptr{
        unsafe.Offsetof(gcControllerState{}.fractionalMarkTime),
        unsafe.Offsetof(gcControllerState{}.idleMarkTime),
        unsafe.Offsetof(gcControllerState{}.globalsScan),
-       unsafe.Offsetof(gcControllerState{}.lastStackScan),
        unsafe.Offsetof(timeHistogram{}.underflow),
        unsafe.Offsetof(profBuf{}.overflow),
        unsafe.Offsetof(profBuf{}.overflowTime),

diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 9366bc355f1e49836296d1e09ab0ece2f73ef521..bc4946d46f4eb38db931af1769d4fbcebb5fdd8c 100644 (file)
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -217,7 +217,7 @@ type gcControllerState struct {
 
        // lastStackScan is the number of bytes of stack that were scanned
        // last GC cycle.
-       lastStackScan uint64
+       lastStackScan atomic.Uint64
 
        // maxStackScan is the amount of allocated goroutine stack space in
        // use by goroutines.
@@ -557,7 +557,7 @@ func (c *gcControllerState) revise() {
 
        // The expected scan work is computed as the amount of bytes scanned last
        // GC cycle (both heap and stack), plus our estimate of globals work for this cycle.
-       scanWorkExpected := int64(c.lastHeapScan + c.lastStackScan + c.globalsScan)
+       scanWorkExpected := int64(c.lastHeapScan + c.lastStackScan.Load() + c.globalsScan)
 
        // maxScanWork is a worst-case estimate of the amount of scan work that
        // needs to be performed in this GC cycle. Specifically, it represents
@@ -740,7 +740,7 @@ func (c *gcControllerState) endCycle(now int64, procs int, userForced bool) {
                printlock()
                goal := gcGoalUtilization * 100
                print("pacer: ", int(utilization*100), "% CPU (", int(goal), " exp.) for ")
-               print(c.heapScanWork.Load(), "+", c.stackScanWork.Load(), "+", c.globalsScanWork.Load(), " B work (", c.lastHeapScan+c.lastStackScan+c.globalsScan, " B exp.) ")
+               print(c.heapScanWork.Load(), "+", c.stackScanWork.Load(), "+", c.globalsScanWork.Load(), " B work (", c.lastHeapScan+c.lastStackScan.Load()+c.globalsScan, " B exp.) ")
                live := c.heapLive.Load()
                print("in ", c.triggered, " B -> ", live, " B (∆goal ", int64(live)-int64(c.lastHeapGoal), ", cons/mark ", oldConsMark, ")")
                if !ok {
@@ -892,7 +892,7 @@ func (c *gcControllerState) resetLive(bytesMarked uint64) {
        c.heapLive.Store(bytesMarked)
        c.heapScan.Store(uint64(c.heapScanWork.Load()))
        c.lastHeapScan = uint64(c.heapScanWork.Load())
-       c.lastStackScan = uint64(c.stackScanWork.Load())
+       c.lastStackScan.Store(uint64(c.stackScanWork.Load()))
        c.triggered = ^uint64(0) // Reset triggered.
 
        // heapLive was updated, so emit a trace event.
@@ -1257,7 +1257,7 @@ func (c *gcControllerState) commit(isSweepDone bool) {
        // plus additional runway for non-heap sources of GC work.
        gcPercentHeapGoal := ^uint64(0)
        if gcPercent := c.gcPercent.Load(); gcPercent >= 0 {
-               gcPercentHeapGoal = c.heapMarked + (c.heapMarked+atomic.Load64(&c.lastStackScan)+atomic.Load64(&c.globalsScan))*uint64(gcPercent)/100
+               gcPercentHeapGoal = c.heapMarked + (c.heapMarked+c.lastStackScan.Load()+atomic.Load64(&c.globalsScan))*uint64(gcPercent)/100
        }
        // Apply the minimum heap size here. It's defined in terms of gcPercent
        // and is only updated by functions that call commit.
@@ -1289,7 +1289,7 @@ func (c *gcControllerState) commit(isSweepDone bool) {
        // Furthermore, by setting the runway so that CPU resources are divided
        // this way, assuming that the cons/mark ratio is correct, we make that
        // division a reality.
-       c.runway.Store(uint64((c.consMark * (1 - gcGoalUtilization) / (gcGoalUtilization)) * float64(c.lastHeapScan+c.lastStackScan+c.globalsScan)))
+       c.runway.Store(uint64((c.consMark * (1 - gcGoalUtilization) / (gcGoalUtilization)) * float64(c.lastHeapScan+c.lastStackScan.Load()+c.globalsScan)))
 }
 
 // setGCPercent updates gcPercent. commit must be called after.