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Optimize error path in FiberRuntime #9975

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Merged
merged 3 commits into from
Jun 19, 2025
Merged

Optimize error path in FiberRuntime #9975

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ba4d980
Optimize error path in FiberRuntime
kyri-petrou Jun 16, 2025
01aaafe
PR comments
kyri-petrou Jun 18, 2025
7029103
Merge branch 'series/2.x' into optimize-error-path-fiber-runtime
kyri-petrou Jun 19, 2025
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45 changes: 32 additions & 13 deletions core/shared/src/main/scala/zio/internal/FiberRuntime.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -538,21 +538,29 @@ final class FiberRuntime[E, A](fiberId: FiberId.Runtime, fiberRefs0: FiberRefs,
val stack = _stack
val size = _stackSize // racy

builder += _lastTrace
var last = _lastTrace
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Much more performant to keep the last variable in the stack memory instead of checking it in StackTraceBuilder which kept it in the heap

builder += last

try {
if (stack ne null) {
var i = (if (stack.length < size) stack.length else size) - 1

while (i >= 0) {
val k = stack(i)
if (k ne null) { // racy
builder += k.trace
val trace = k.trace
if (trace ne last) {
last = trace
builder += trace
}
i -= 1
}
}
}

builder += id.location // TODO: Allow parent traces?
val loc = id.location
if (loc ne last)
builder += loc // TODO: Allow parent traces?

StackTrace(self.fiberId, builder.result())
} finally {
Expand Down Expand Up @@ -844,19 +852,27 @@ final class FiberRuntime[E, A](fiberId: FiberId.Runtime, fiberRefs0: FiberRefs,
*
* '''NOTE''': This method must be invoked by the fiber itself.
*/
private def patchRuntimeFlags[R, E, A](
private def patchRuntimeFlags[E0, A0](
patch: RuntimeFlags.Patch,
cause: Cause[E0],
continueEffect: Exit[E0, A0]
): Exit[E0, A0] =
patchRuntimeFlagsCause(patch, cause) match {
case null => continueEffect
case c => Exit.Failure(c)
}

private def patchRuntimeFlagsCause[E0](
patch: RuntimeFlags.Patch,
cause: Cause[E],
continueEffect: ZIO[R, E, A]
): ZIO[R, E, A] = {
cause: Cause[E0]
): Cause[E0] = {
val changed = patchRuntimeFlagsOnly(patch)
val interruptEnabled = RuntimeFlags.Patch.isEnabled(patch, RuntimeFlag.Interruption.mask)

if (changed && interruptEnabled && shouldInterrupt()) {
if (cause ne null) Exit.Failure(cause ++ getInterruptedCause())
else Exit.Failure(getInterruptedCause())
} else if (cause ne null) Exit.Failure(cause)
else continueEffect
if (cause ne null) cause ++ getInterruptedCause()
else getInterruptedCause()
} else cause
}

/**
Expand Down Expand Up @@ -1241,12 +1257,15 @@ final class FiberRuntime[E, A](fiberId: FiberId.Runtime, fiberRefs0: FiberRefs,
}

case updateFlags: ZIO.UpdateRuntimeFlags =>
cur = patchRuntimeFlags(updateFlags.update, cause, null)
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@kyri-petrou kyri-petrou Jun 16, 2025 •
edited
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This would have previously:

  1. Allocated an Exit.Failure unnecessarily
  2. Set cur = Exit.Failure(cause) which means we would have to exit the inner loop (due to the cur ne null condition), only so that we would do another loop of the outer loop to end back at the Exit.Failure case

cause = patchRuntimeFlagsCause(updateFlags.update, cause)
}
}

if (cur eq null) {
return failure
val f =
if (cause eq failure.cause) failure
else Exit.Failure(cause)
return f
}

case updateRuntimeFlags: UpdateRuntimeFlags =>
Expand Down
15 changes: 6 additions & 9 deletions core/shared/src/main/scala/zio/internal/StackTraceBuilder.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -22,19 +22,16 @@ import scala.collection.mutable.ArrayBuilder
import scala.reflect.ClassTag

private[zio] class StackTraceBuilder private () { self =>
private var last: Trace = null.asInstanceOf[Trace]
private val builder = new ArrayBuilder.ofRef()(ClassTag.AnyRef.asInstanceOf[ClassTag[Trace]])
private[this] val builder = new ArrayBuilder.ofRef()(ClassTag.AnyRef.asInstanceOf[ClassTag[Trace]])

def +=(trace: Trace): Unit =
if ((trace ne null) && (trace ne Trace.empty) && (trace ne last)) {
def +=(trace: Trace): Unit = {
if ((trace ne null) && (trace ne Trace.empty))
builder += trace
last = trace
}
()
}

def clear(): Unit = {
def clear(): Unit =
builder.clear()
last = null.asInstanceOf[Trace]
}

def result(): Chunk[Trace] =
Chunk.fromArray(builder.result())
Expand Down