runtime: use atomic.Float64 for assist ratio
Change-Id: Ie7f09a7c9545ef9dd1860b1e332c4edbcbf8165e
Reviewed-on: https://go-review.googlesource.com/c/go/+/356170
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Knyszek <mknyszek@google.com>
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index 246907e..efda65f 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -400,8 +400,8 @@
// balance positive. When the required amount of work is low,
// we over-assist to build up credit for future allocations
// and amortize the cost of assisting.
- assistWorkPerByte := float64frombits(atomic.Load64(&gcController.assistWorkPerByte))
- assistBytesPerWork := float64frombits(atomic.Load64(&gcController.assistBytesPerWork))
+ assistWorkPerByte := gcController.assistWorkPerByte.Load()
+ assistBytesPerWork := gcController.assistBytesPerWork.Load()
debtBytes := -gp.gcAssistBytes
scanWork := int64(assistWorkPerByte * float64(debtBytes))
if scanWork < gcOverAssistWork {
@@ -545,7 +545,7 @@
// this scan work counts for. The "1+" is a poor man's
// round-up, to ensure this adds credit even if
// assistBytesPerWork is very low.
- assistBytesPerWork := float64frombits(atomic.Load64(&gcController.assistBytesPerWork))
+ assistBytesPerWork := gcController.assistBytesPerWork.Load()
gp.gcAssistBytes += 1 + int64(assistBytesPerWork*float64(workDone))
// If this is the last worker and we ran out of work,
@@ -638,7 +638,7 @@
return
}
- assistBytesPerWork := float64frombits(atomic.Load64(&gcController.assistBytesPerWork))
+ assistBytesPerWork := gcController.assistBytesPerWork.Load()
scanBytes := int64(float64(scanWork) * assistBytesPerWork)
lock(&work.assistQueue.lock)
@@ -672,7 +672,7 @@
if scanBytes > 0 {
// Convert from scan bytes back to work.
- assistWorkPerByte := float64frombits(atomic.Load64(&gcController.assistWorkPerByte))
+ assistWorkPerByte := gcController.assistWorkPerByte.Load()
scanWork = int64(float64(scanBytes) * assistWorkPerByte)
atomic.Xaddint64(&gcController.bgScanCredit, scanWork)
}
diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 9338359..342ea41 100644
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -222,24 +222,14 @@
// bytes that should be performed by mutator assists. This is
// computed at the beginning of each cycle and updated every
// time heapScan is updated.
- //
- // Stored as a uint64, but it's actually a float64. Use
- // float64frombits to get the value.
- //
- // Read and written atomically.
- assistWorkPerByte uint64
+ assistWorkPerByte atomic.Float64
// assistBytesPerWork is 1/assistWorkPerByte.
//
- // Stored as a uint64, but it's actually a float64. Use
- // float64frombits to get the value.
- //
- // Read and written atomically.
- //
// Note that because this is read and written independently
// from assistWorkPerByte users may notice a skew between
// the two values, and such a state should be safe.
- assistBytesPerWork uint64
+ assistBytesPerWork atomic.Float64
// fractionalUtilizationGoal is the fraction of wall clock
// time that should be spent in the fractional mark worker on
@@ -333,7 +323,7 @@
c.revise()
if debug.gcpacertrace > 0 {
- assistRatio := float64frombits(atomic.Load64(&c.assistWorkPerByte))
+ assistRatio := c.assistWorkPerByte.Load()
print("pacer: assist ratio=", assistRatio,
" (scan ", gcController.heapScan>>20, " MB in ",
work.initialHeapLive>>20, "->",
@@ -439,8 +429,8 @@
// cycle.
assistWorkPerByte := float64(scanWorkRemaining) / float64(heapRemaining)
assistBytesPerWork := float64(heapRemaining) / float64(scanWorkRemaining)
- atomic.Store64(&c.assistWorkPerByte, float64bits(assistWorkPerByte))
- atomic.Store64(&c.assistBytesPerWork, float64bits(assistBytesPerWork))
+ c.assistWorkPerByte.Store(assistWorkPerByte)
+ c.assistBytesPerWork.Store(assistBytesPerWork)
}
// endCycle computes the trigger ratio for the next cycle.
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c14a1f1..b80f09f 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -3646,7 +3646,7 @@
// Flush assist credit to the global pool. This gives
// better information to pacing if the application is
// rapidly creating an exiting goroutines.
- assistWorkPerByte := float64frombits(atomic.Load64(&gcController.assistWorkPerByte))
+ assistWorkPerByte := gcController.assistWorkPerByte.Load()
scanCredit := int64(assistWorkPerByte * float64(gp.gcAssistBytes))
atomic.Xaddint64(&gcController.bgScanCredit, scanCredit)
gp.gcAssistBytes = 0
