Code size analysis#

pw_async2: Cooperative async tasks for embedded

Core async2 implementation#

The following table shows the code size cost of adding pw_async2 to a system. These size reports assume a baseline system with an RTOS which already uses a handful of core Pigweed components including HAL abstractions and pw_allocator.

The first row captures the core of pw_async2: the dispatcher, tasks, and wakers, using the pw_async2_basic dispatcher backend. This is the minimum size cost a system must pay to adopt pw_async2. The following row demonstrates the cost of adding another task to this system. Of course, the majority of the cost of the task exists within its implementation — this simply shows that there is minimal internal overhead.

Label

Segment

Delta

Full cost of including pw_async2

FLASH

	+628	[section .rodata]
	+4	[section .text]
	-12	vClearInterruptMaskFromISR
	-4	__bi_84
	+208	pw::async2::size_report::Measure()
	-2	pw::containers::internal::IntrusiveForwardListItem::DoGetPrevious()
	+16	pw::containers::internal::LegacyIntrusiveList<>::push_back()
NEW	+384	pw::async2::NativeDispatcherBase::RunOneTask()
NEW	+140	pw::async2::NativeDispatcherBase::NativeDispatcherBase()
NEW	+116	pw::async2::NativeDispatcherBase::Post()
NEW	+112	pw::async2::backend::NativeDispatcher::DoRunToCompletion()
NEW	+104	pw::async2::Task::Deregister()
NEW	+96	_ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS8_EEDTclsr3stdE9__declvalISB_ELi0EEEvEEEE10OutputTypeEEERSB_
NEW	+96	pw::async2::Task::TryDeregister()
NEW	+96	pw::async2::backend::NativeDispatcher::DoRunUntilStalled()
NEW	+92	pw::async2::NativeDispatcherBase::WakeTask()
NEW	+72	pw::async2::size_report::PendableValue<>::Get()
NEW	+68	pw::async2::NativeDispatcherBase::AttemptRequestWake()
NEW	+60	pw::async2::MemberPendableWrapper<>::Pend()
NEW	+56	pw::async2::Waker::operator=()
NEW	+56	pw::async2::size_report::MockTask::DoPend()
NEW	+52	pw::async2::internal::CloneWaker()
NEW	+48	pw::async2::size_report::MockTask::~MockTask()
NEW	+40	pw::async2::Waker::Wake()
NEW	+38	pw::async2::Task::~Task()
NEW	+36	pw::async2::Waker::InternalCloneIntoLocked()
NEW	+32	pw::async2::Waker::InsertIntoTaskWakerList()
NEW	+32	pw::async2::Waker::RemoveFromTaskWakerList()
NEW	+32	pw::async2::backend::NativeDispatcher::NativeDispatcher()
NEW	+30	pw::async2::internal::PendableAsTaskWithOutput<>::DoPend()
NEW	+26	pw::async2::Task::RemoveAllWakersLocked()
NEW	+24	_ZNSt3__28__invokeB8nn210000IMN2pw6async211size_report13PendableValueIiEEFNS2_4PollIiEERNS2_7ContextEERPS5_JS9_EvEEDTcldsdeclsr3stdE7declvalIT0_EEclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT1_EEEEOSF_OSE_DpOSG_
NEW	+24	pw::async2::Dispatcher::RunUntilStalled()
NEW	+24	pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>()
NEW	+24	pw::async2::NativeDispatcherBase::Wake()
NEW	+24	pw::async2::Task
NEW	+24	pw::async2::internal::PendableAsTaskWithOutput<>
NEW	+24	pw::async2::size_report::MockTask
NEW	+24	pw::async2::size_report::MockTask::DoPend()::{lambda()#1}::operator()()
NEW	+24	pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()()
NEW	+24	pw::containers::internal::IntrusiveListItemBase<>::unlist()
NEW	+22	pw::async2::NativeDispatcherBase::PopWokenTask()
NEW	+20	pw::IntrusiveForwardList<>::pop_front()
NEW	+18	pw::containers::internal::LegacyIntrusiveList<>::Item::~Item()
NEW	+16	_GLOBAL__sub_I_async2_core.cc
NEW	+16	pw::async2::Task::RemoveWakerLocked()
NEW	+16	pw::async2::Waker::InsertIntoTaskWakerListLocked()
NEW	+16	pw::async2::Waker::RemoveFromTaskWakerListLocked()
NEW	+16	pw::async2::Waker::Waker()
NEW	+16	pw::async2::Waker::~Waker()
NEW	+14	pw::async2::internal::PendableAsTaskWithOutput<>::~PendableAsTaskWithOutput()
NEW	+12	pw::async2::Dispatcher::RunToCompletion()
NEW	+12	pw::async2::NativeDispatcherBase
NEW	+12	pw::async2::NativeDispatcherBase::RemoveSleepingTaskLocked()
NEW	+12	pw::async2::NativeDispatcherBase::RemoveWokenTaskLocked()
NEW	+12	pw::async2::Task::AddWakerLocked()
NEW	+12	pw::async2::backend::NativeDispatcher
NEW	+12	pw::async2::backend::NativeDispatcher::DoWake()
NEW	+12	pw::async2::internal::StoreWaker()
NEW	+8	pw::async2::size_report::MockTask::DoDestroy()
NEW	+2	pw::async2::Task::DoDestroy()

+3,268

+168

Base incremental cost of adding a task to an existing async system

+48

async2 utilities#

Pigweed provides several utilities to simplify writing asynchronous code. Among these are combinators which operate over several pendables, such as Join which waits for all pendables to complete, and Select which waits for the first pendable to complete.

The table below demonstrates the code size impact of using these utilities. For both Join and Select, the report shows:

The initial cost of using the utility with multiple pendables of the same type.
The incremental cost of adding a second call with pendables of different types, which demonstrates the overhead of template specialization.

Additionally, the table includes a comparison showing the code size difference between using the Select helper versus manually polling each pendable.

Label

Segment

Delta

Size of calling Select() with several pendables of the same type

FLASH

	+56	[section .rodata]
	-76	pw::async2::size_report::Measure()
DEL	-96	_ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS8_EEDTclsr3stdE9__declvalISB_ELi0EEEvEEEE10OutputTypeEEERSB_
	+4	pw::async2::internal::PendableAsTaskWithOutput<>::DoPend()
	-12	pw::async2::Dispatcher::RunUntilStalled()
	+16	pw::async2::internal::PendableAsTaskWithOutput<>
DEL	-16	_GLOBAL__sub_I_async2_core.cc
	-6	operator delete()
	+12	vClearInterruptMaskFromISR
NEW	+194	pw::async2::Selector<>::PendFrom<>()
NEW	+188	pw::async2::size_report::SingleTypeSelect()
NEW	+96	_ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_8SelectorIJNS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEESA_SA_EEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS9_EEDTclsr3stdE9__declvalISD_ELi0EEEvEEEE10OutputTypeEEERSD_
NEW	+16	_GLOBAL__sub_I_select.cc
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_0NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_1OZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_0NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_1OZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_0NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_1OZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_0NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_1OZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+12	_ZNSt3__220__throw_if_valuelessB8nn210000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EiEENS4_ILj2EiEENS3_21AllPendablesCompletedEEEEEEEvDpOT_
NEW	+12	_ZNSt3__226__throw_bad_variant_accessB8nn210000Ev
NEW	+10	pw::async2::Selector<>::Pend()
NEW	+6	std::__2::__libcpp_verbose_abort()

+472

Size of an additional a call to Select() with pendables of different types

FLASH

	+182	pw::async2::Selector<>::PendFrom<>()
	+8	pw::async2::size_report::Measure()
	+140	pw::async2::size_report::PendableValue<>::Get()
	+116	pw::async2::MemberPendableWrapper<>::Pend()
	+40	pw::async2::internal::PendableAsTaskWithOutput<>
	+34	pw::async2::internal::PendableAsTaskWithOutput<>::DoPend()
	+48	pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>()
	+48	pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()()
	-8	vClearInterruptMaskFromISR
	+14	pw::async2::internal::PendableAsTaskWithOutput<>::~PendableAsTaskWithOutput()
	+10	pw::async2::Selector<>::Pend()
NEW	+188	pw::async2::size_report::MultiTypeSelect()
NEW	+96	_ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_8SelectorIJNS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEENS4_IXadL_ZNS6_IjE3GetES9_EEEENS4_IXadL_ZNS6_IcE3GetES9_EEEEEEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS9_EEDTclsr3stdE9__declvalISH_ELi0EEEvEEEE10OutputTypeEEERSH_
NEW	+24	_ZNSt3__28__invokeB8nn210000IMN2pw6async211size_report13PendableValueIcEEFNS2_4PollIcEERNS2_7ContextEERPS5_JS9_EvEEDTcldsdeclsr3stdE7declvalIT0_EEclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT1_EEEEOSF_OSE_DpOSG_
NEW	+24	_ZNSt3__28__invokeB8nn210000IMN2pw6async211size_report13PendableValueIjEEFNS2_4PollIjEERNS2_7ContextEERPS5_JS9_EvEEDTcldsdeclsr3stdE7declvalIT0_EEclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT1_EEEEOSF_OSE_DpOSG_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_0NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_1OZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_0NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_1OZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_0NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_1OZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+14	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_0NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_1OZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_
NEW	+12	_ZNSt3__220__throw_if_valuelessB8nn210000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EjEENS4_ILj2EcEENS3_21AllPendablesCompletedEEEEEEEvDpOT_

+1,032

Cost of using Select() versus manually polling each pendable

FLASH

	+56	[section .rodata]
	-62	pw::async2::size_report::SelectComparison::Pend()
	+116	pw::async2::MemberPendableWrapper<>::Pend()
	-2	pw::async2::internal::PendableAsTaskWithOutput<>::DoPend()
	+16	pw::async2::internal::PendableAsTaskWithOutput<>
	+48	pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>()
	-8	vClearInterruptMaskFromISR
	-6	operator delete()
NEW	+180	pw::async2::Selector<>::PendFrom<>()
NEW	+72	pw::async2::size_report::SelectComparison::Pend()::{lambda()#1}::operator()()
NEW	+36	pw::async2::internal::VisitSelectResult<>()::{lambda()#1}::operator()<>()
NEW	+32	_ZNSt3__216__variant_detail12__visitation9__variant13__visit_valueB8nn210000IZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_JSF_EEEDcSU_DpOT0_
NEW	+24	_ZNSt3__28__invokeB8nn210000IMN2pw6async211size_report13PendableValueIcEEFNS2_4PollIcEERNS2_7ContextEERPS5_JS9_EvEEDTcldsdeclsr3stdE7declvalIT0_EEclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT1_EEEEOSF_OSE_DpOSG_
NEW	+24	_ZNSt3__28__invokeB8nn210000IMN2pw6async211size_report13PendableValueIjEEFNS2_4PollIjEERNS2_7ContextEERPS5_JS9_EvEEDTcldsdeclsr3stdE7declvalIT0_EEclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT1_EEEEOSF_OSE_DpOSG_
NEW	+22	_ZNSt3__25visitB8nn210000IZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS2_12SelectResultILj0EiEENS6_ILj1EjEENS6_ILj2EcEENS2_21AllPendablesCompletedEEEEZNS2_11size_report16SelectComparison4PendERNS2_7ContextEEUlSA_E_NS_5tupleIJOZNSE_4PendESG_EUliE_OZNSE_4PendESG_EUljE_OZNSE_4PendESG_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSR_E_JSC_EvEEDcSR_DpOT0_
NEW	+18	pw::async2::VisitSelectResult<>()
NEW	+18	pw::async2::internal::VisitSelectResult<>()
NEW	+12	_ZNSt3__220__throw_if_valuelessB8nn210000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EjEENS4_ILj2EcEENS3_21AllPendablesCompletedEEEEEEEvDpOT_
NEW	+12	_ZNSt3__226__throw_bad_variant_accessB8nn210000Ev
NEW	+12	_ZNSt3__28__invokeB8nn210000IZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUliE_JiEEEDTclclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOS8_DpOS9_
NEW	+10	_ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn210000IJRNS0_5__altILj0ESA_EEEEEDcDpOT_
NEW	+10	_ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn210000IJRNS0_5__altILj1ESB_EEEEEDcDpOT_
NEW	+10	_ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn210000IJRNS0_5__altILj2ESC_EEEEEDcDpOT_
NEW	+10	_ZNSt3__28__invokeB8nn210000IZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUlcE_JcEEEDTclclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOS8_DpOS9_
NEW	+10	_ZNSt3__28__invokeB8nn210000IZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUljE_JjEEEDTclclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOS8_DpOS9_
NEW	+10	pw::async2::Selector<>::Pend()
NEW	+8	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_
NEW	+8	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_
NEW	+8	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_
NEW	+6	std::__2::__libcpp_verbose_abort()
NEW	+2	_ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn210000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_

+712

Size of calling Join() with several pendables of the same type

+368

Size of an additional a call to Join() with pendables of different types

+1,016

OnceSender and OnceReceiver#

The next table shows sizes of the pair of OnceSender and OnceReceiver types, which allow for returning a delayed result from an async function, similar to a Future type in other languages. This type is templated on its stored value, causing specialization overhead for each type sent through the sender/receiver pair. The first row showcases the base cost of using a OnceSender and OnceReceiver; the second row adds another template specialization on top of this to demonstrate the incremental cost.

Label

Segment

Delta

Size of OnceSender / OnceReceiver

+960

Cost of additional OnceSender / OnceReceiver template specialization

+776