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Optimize event emission#4334

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bastian/optimize-event-emission
Nov 13, 2025
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Optimize event emission#4334
turbolent merged 1 commit into
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bastian/optimize-event-emission

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@turbolent turbolent commented Nov 12, 2025 •
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Looking at the optimizations of the FastBreak contract (dapperlabs/nba-smart-contracts#294) I noticed this change to an event parameter: https://github.com/dapperlabs/nba-smart-contracts/pull/294/files#diff-9f296e6a8c507b02a639681b7295fafccaf5868f24299c03efda0bde31a18047L68.

Given the event emission handler exports the event arguments immediately, we can avoid transfers (copies) in general.

  • Targeted PR against master branch
  • Linked to Github issue with discussion and accepted design OR link to spec that describes this work
  • Code follows the standards mentioned here
  • Updated relevant documentation
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@turbolent
optimize event emission
1ea9980 
only convert arguments, do not transfer (avoid unnecessary copies)
@turbolent turbolent self-assigned this Nov 12, 2025
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github-actions Bot commented Nov 12, 2025

Benchstat comparison

  • Base branch: onflow:master
  • Base commit: 7104cac
Results

old.txtnew.txt
time/opdelta
pkg:github.com/onflow/cadence/bbq/compiler goos:linux goarch:amd64
CompileTime-433.4µs ± 0%32.6µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4408µs ± 0%402µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-4192µs ± 0%198µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-4261ns ± 0%260ns ± 0%~(p=1.000 n=1+1)
ExportType/simple_type-477.9ns ± 0%77.8ns ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-4121µs ± 0%117µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-420.9µs ± 0%21.0µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-415.0µs ± 0%14.9µs ± 0%~(p=1.000 n=1+1)
ImperativeFibNewCompilerNewVM-435.2µs ± 0%35.2µs ± 0%~(p=1.000 n=1+1)
ImperativeFibNewVM-417.4µs ± 0%17.3µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-42.23ms ± 0%2.14ms ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-4111µs ± 0%116µs ± 0%~(p=1.000 n=1+1)
InterpreterImperativeFib-421.9µs ± 0%22.5µs ± 0%~(p=1.000 n=1+1)
InterpreterNewStruct-463.5µs ± 0%61.4µs ± 0%~(p=1.000 n=1+1)
MethodCall/concrete_type_method_call-429.3µs ± 0%29.3µs ± 0%~(p=1.000 n=1+1)
MethodCall/interface_method_call-451.0µs ± 0%51.1µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-41.04µs ± 0%1.07µs ± 0%~(p=1.000 n=1+1)
NewInterpreter/new_sub-interpreter-4337ns ± 0%314ns ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-487.3µs ± 0%86.6µs ± 0%~(p=1.000 n=1+1)
NewStruct-434.6µs ± 0%34.5µs ± 0%~(p=1.000 n=1+1)
NewStructRaw-43.69µs ± 0%3.80µs ± 0%~(p=1.000 n=1+1)
RecursionFib-4848µs ± 0%858µs ± 0%~(p=1.000 n=1+1)
RuntimeFungibleTokenTransfer-4725µs ± 0%722µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4590µs ± 0%579µs ± 0%~(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4632µs ± 0%629µs ± 0%~(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-42.61ms ± 0%2.58ms ± 0%~(p=1.000 n=1+1)
RuntimeResourceTracking-411.6ms ± 0%11.5ms ± 0%~(p=1.000 n=1+1)
RuntimeScriptNoop-414.6µs ± 0%14.8µs ± 0%~(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-427.6µs ± 0%27.6µs ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-466.9ns ± 0%65.9ns ± 0%~(p=1.000 n=1+1)
 
alloc/opdelta
pkg:github.com/onflow/cadence/bbq/compiler goos:linux goarch:amd64
CompileTime-416.3kB ± 0%16.3kB ± 0%~(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4152kB ± 0%153kB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-473.6kB ± 0%73.6kB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-4120B ± 0%120B ± 0%~(all equal)
ExportType/simple_type-40.00B 0.00B ~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-438.2kB ± 0%38.1kB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-48.30kB ± 0%8.30kB ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-41.94kB ± 0%1.94kB ± 0%~(all equal)
ImperativeFibNewCompilerNewVM-421.8kB ± 0%21.8kB ± 0%~(all equal)
ImperativeFibNewVM-44.68kB ± 0%4.68kB ± 0%~(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-41.19MB ± 0%1.19MB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-439.9kB ± 0%39.9kB ± 0%~(p=1.000 n=1+1)
InterpreterImperativeFib-48.29kB ± 0%8.29kB ± 0%~(all equal)
InterpreterNewStruct-424.3kB ± 0%24.4kB ± 0%~(p=1.000 n=1+1)
MethodCall/concrete_type_method_call-47.02kB ± 0%7.00kB ± 0%~(p=1.000 n=1+1)
MethodCall/interface_method_call-414.5kB ± 0%14.5kB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-4976B ± 0%976B ± 0%~(all equal)
NewInterpreter/new_sub-interpreter-4232B ± 0%232B ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-440.3kB ± 0%40.3kB ± 0%~(all equal)
NewStruct-410.4kB ± 0%10.3kB ± 0%~(p=1.000 n=1+1)
NewStructRaw-42.58kB ± 0%2.56kB ± 0%~(p=1.000 n=1+1)
RecursionFib-488.1kB ± 0%88.1kB ± 0%~(all equal)
RuntimeFungibleTokenTransfer-4238kB ± 0%238kB ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4159kB ± 0%160kB ± 0%~(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4173kB ± 0%173kB ± 0%~(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-41.76MB ± 0%1.76MB ± 0%~(p=1.000 n=1+1)
RuntimeResourceTracking-49.26MB ± 0%9.27MB ± 0%~(p=1.000 n=1+1)
RuntimeScriptNoop-48.04kB ± 0%8.04kB ± 0%~(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-49.79kB ± 0%9.79kB ± 0%~(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-448.0B ± 0%48.0B ± 0%~(all equal)
 
allocs/opdelta
pkg:github.com/onflow/cadence/bbq/compiler goos:linux goarch:amd64
CompileTime-4176 ± 0%176 ± 0%~(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-42.46k ± 0%2.46k ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-4931 ± 0%931 ± 0%~(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-43.00 ± 0%3.00 ± 0%~(all equal)
ExportType/simple_type-40.00 0.00 ~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-4978 ± 0%966 ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4176 ± 0%176 ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-449.0 ± 0%49.0 ± 0%~(all equal)
ImperativeFibNewCompilerNewVM-4205 ± 0%205 ± 0%~(all equal)
ImperativeFibNewVM-486.0 ± 0%86.0 ± 0%~(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-417.7k ± 0%17.7k ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-4837 ± 0%833 ± 0%~(p=1.000 n=1+1)
InterpreterImperativeFib-4175 ± 0%175 ± 0%~(all equal)
InterpreterNewStruct-4418 ± 0%418 ± 0%~(all equal)
MethodCall/concrete_type_method_call-4135 ± 0%135 ± 0%~(all equal)
MethodCall/interface_method_call-4285 ± 0%285 ± 0%~(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-415.0 ± 0%15.0 ± 0%~(all equal)
NewInterpreter/new_sub-interpreter-44.00 ± 0%4.00 ± 0%~(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-4722 ± 0%722 ± 0%~(all equal)
NewStruct-4219 ± 0%219 ± 0%~(all equal)
NewStructRaw-438.0 ± 0%38.0 ± 0%~(all equal)
RecursionFib-43.65k ± 0%3.65k ± 0%~(all equal)
RuntimeFungibleTokenTransfer-44.00k ± 0%3.98k ± 0%~(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-42.99k ± 0%2.98k ± 0%~(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-43.01k ± 0%3.00k ± 0%~(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-436.7k ± 0%36.7k ± 0%~(all equal)
RuntimeResourceTracking-4159k ± 0%159k ± 0%~(p=1.000 n=1+1)
RuntimeScriptNoop-4113 ± 0%113 ± 0%~(all equal)
RuntimeVMInvokeContractImperativeFib-4197 ± 0%197 ± 0%~(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-41.00 ± 0%1.00 ± 0%~(all equal)
 

SupunS
SupunS approved these changes Nov 12, 2025
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Good idea!

@turbolent turbolent merged commit a942168 into master Nov 13, 2025
12 of 15 checks passed
@turbolent turbolent deleted the bastian/optimize-event-emission branch November 13, 2025 00:05
@BrewTestBot BrewTestBot mentioned this pull request Nov 20, 2025
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@SupunS SupunS SupunS approved these changes

@RZhang05 RZhang05 Awaiting requested review from RZhang05

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