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runtime: convert gcController.globalsScan to atomic type

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For #53821.

Change-Id: I92bd33e355c868ae229395fd9c98fdb10768d03d
Reviewed-on: https://go-review.googlesource.com/c/go/+/417779
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Michael Pratt 2022-07-15 14:33:16 -04:00
parent 02fb9b8ca9
commit b8f4847d6f
4 changed files with 9 additions and 12 deletions
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1
src/runtime/align_runtime_test.go
View File

@ -26,7 +26,6 @@ var AtomicFields = []uintptr{
unsafe.Offsetof(gcControllerState{}.dedicatedMarkWorkersNeeded),
unsafe.Offsetof(gcControllerState{}.fractionalMarkTime),
unsafe.Offsetof(gcControllerState{}.idleMarkTime),
unsafe.Offsetof(gcControllerState{}.globalsScan),
unsafe.Offsetof(timeHistogram{}.underflow),
unsafe.Offsetof(profBuf{}.overflow),
unsafe.Offsetof(profBuf{}.overflowTime),

2
src/runtime/export_test.go
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@ -1323,7 +1323,7 @@ func (c *GCController) StartCycle(stackSize, globalsSize uint64, scannableFrac f
trigger = c.heapMarked
}
c.maxStackScan.Store(stackSize)
c.globalsScan = globalsSize
c.globalsScan.Store(globalsSize)
c.heapLive.Store(trigger)
c.heapScan.Add(int64(float64(trigger-c.heapMarked) * scannableFrac))
c.startCycle(0, gomaxprocs, gcTrigger{kind: gcTriggerHeap})

2
src/runtime/mgc.go
View File

@ -1121,7 +1121,7 @@ func gcMarkTermination() {
work.heap0>>20, "->", work.heap1>>20, "->", work.heap2>>20, " MB, ",
gcController.lastHeapGoal>>20, " MB goal, ",
gcController.maxStackScan.Load()>>20, " MB stacks, ",
gcController.globalsScan>>20, " MB globals, ",
gcController.globalsScan.Load()>>20, " MB globals, ",
work.maxprocs, " P")
if work.userForced {
print(" (forced)")

16
src/runtime/mgcpacer.go
View File

@ -231,9 +231,7 @@ type gcControllerState struct {
// globalsScan is the total amount of global variable space
// that is scannable.
//
// Read and updated atomically.
globalsScan uint64
globalsScan atomic.Uint64
// heapMarked is the number of bytes marked by the previous
// GC. After mark termination, heapLive == heapMarked, but
@ -555,14 +553,14 @@ 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.Load() + c.globalsScan)
scanWorkExpected := int64(c.lastHeapScan + c.lastStackScan.Load() + c.globalsScan.Load())
// maxScanWork is a worst-case estimate of the amount of scan work that
// needs to be performed in this GC cycle. Specifically, it represents
// the case where *all* scannable memory turns out to be live, and
// *all* allocated stack space is scannable.
maxStackScan := c.maxStackScan.Load()
maxScanWork := int64(scan + maxStackScan + c.globalsScan)
maxScanWork := int64(scan + maxStackScan + c.globalsScan.Load())
if work > scanWorkExpected {
// We've already done more scan work than expected. Because our expectation
// is based on a steady-state scannable heap size, we assume this means our
@ -738,7 +736,7 @@ 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.Load()+c.globalsScan, " B exp.) ")
print(c.heapScanWork.Load(), "+", c.stackScanWork.Load(), "+", c.globalsScanWork.Load(), " B work (", c.lastHeapScan+c.lastStackScan.Load()+c.globalsScan.Load(), " B exp.) ")
live := c.heapLive.Load()
print("in ", c.triggered, " B -> ", live, " B (∆goal ", int64(live)-int64(c.lastHeapGoal), ", cons/mark ", oldConsMark, ")")
if !ok {
@ -953,7 +951,7 @@ func (c *gcControllerState) addScannableStack(pp *p, amount int64) {
}
func (c *gcControllerState) addGlobals(amount int64) {
atomic.Xadd64(&c.globalsScan, amount)
c.globalsScan.Add(amount)
}
// heapGoal returns the current heap goal.
@ -1255,7 +1253,7 @@ 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+c.lastStackScan.Load()+atomic.Load64(&c.globalsScan))*uint64(gcPercent)/100
gcPercentHeapGoal = c.heapMarked + (c.heapMarked+c.lastStackScan.Load()+c.globalsScan.Load())*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.
@ -1287,7 +1285,7 @@ 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.Load()+c.globalsScan)))
c.runway.Store(uint64((c.consMark * (1 - gcGoalUtilization) / (gcGoalUtilization)) * float64(c.lastHeapScan+c.lastStackScan.Load()+c.globalsScan.Load())))
}
// setGCPercent updates gcPercent. commit must be called after.