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
	RAM NEW +160 pw::async2::size_report::dispatcher NEW +8 pw::async2::impl::dispatcher_lock()::lock	+168
Base incremental cost of adding a task to an existing async system	FLASH +48 pw::async2::size_report::Measure()	+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	FLASH -76 pw::async2::size_report::Measure() DEL -96 _ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS8_EEDTclsr3stdE9__declvalISB_ELi0EEEvEEEE10OutputTypeEEERSB_ +6 pw::async2::internal::PendableAsTaskWithOutput<>::DoPend() -12 pw::async2::Dispatcher::RunUntilStalled() DEL -16 _GLOBAL__sub_I_async2_core.cc +8 vClearInterruptMaskFromISR NEW +152 pw::async2::size_report::SingleTypeJoin() NEW +122 pw::async2::Join<>::PendElement<>() NEW +96 _ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_4JoinIJNS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEESA_SA_EEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS9_EEDTclsr3stdE9__declvalISD_ELi0EEEvEEEE10OutputTypeEEERSD_ NEW +46 pw::async2::Join<>::Pend() NEW +42 pw::async2::Join<>::PendElements<>() NEW +40 _ZNSt3__223__optional_storage_baseINS_5tupleIJOiS2_S2_EEELb0EE13__assign_fromB8nn210000INS_27__optional_move_assign_baseIS3_Lb0EEEEEvOT_ NEW +28 _ZNSt3__227__memberwise_forward_assignB8nn210000INS_5tupleIJOiS2_S2_EEES3_JS2_S2_S2_EJLj0ELj1ELj2EEEEvRT_OT0_NS_13__tuple_typesIJDpT1_EEENS_15__tuple_indicesIJXspT2_EEEE NEW +16 _GLOBAL__sub_I_join.cc NEW +12 _ZNSt3__25tupleIJOiS1_S1_EEaSB8nn210000EOS2_	+368
Size of an additional a call to Join() with pendables of different types	FLASH +8 pw::async2::size_report::Measure() +118 pw::async2::Join<>::PendElement<>() +140 pw::async2::size_report::PendableValue<>::Get() +116 pw::async2::MemberPendableWrapper<>::Pend() +46 pw::async2::Join<>::Pend() +42 pw::async2::Join<>::PendElements<>() +36 pw::async2::internal::PendableAsTaskWithOutput<>::DoPend() +48 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() +24 pw::async2::internal::PendableAsTaskWithOutput<> +48 pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()() -4 vClearInterruptMaskFromISR +14 pw::async2::internal::PendableAsTaskWithOutput<>::~PendableAsTaskWithOutput() NEW +156 pw::async2::size_report::MultiTypeJoin() NEW +96 _ZN2pw6async210Dispatcher23RunPendableUntilStalledINS0_4JoinIJNS0_21MemberPendableWrapperIXadL_ZNS0_11size_report13PendableValueIiE3GetERNS0_7ContextEEEEENS4_IXadL_ZNS6_IjE3GetES9_EEEENS4_IXadL_ZNS6_IcE3GetES9_EEEEEEEEENS0_4PollINDTcldtclsr3stdE7declvalIT_EE4PendclL_ZNSt3__27declvalB8nn210000IS9_EEDTclsr3stdE9__declvalISH_ELi0EEEvEEEE10OutputTypeEEERSH_ NEW +40 _ZNSt3__223__optional_storage_baseINS_5tupleIJOiOjOcEEELb0EE13__assign_fromB8nn210000INS_27__optional_move_assign_baseIS5_Lb0EEEEEvOT_ NEW +28 _ZNSt3__227__memberwise_forward_assignB8nn210000INS_5tupleIJOiOjOcEEES5_JS2_S3_S4_EJLj0ELj1ELj2EEEEvRT_OT0_NS_13__tuple_typesIJDpT1_EEENS_15__tuple_indicesIJXspT2_EEEE 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 +12 _ZNSt3__25tupleIJOiOjOcEEaSB8nn210000EOS4_	+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	FLASH +168 [section .rodata] +84 pw::async2::size_report::Measure() -6 operator delete() +8 vClearInterruptMaskFromISR NEW +112 pw::async2::OnceReceiver<>::Pend() NEW +96 pw::async2::OnceReceiver<>::OnceReceiver() NEW +60 pw::async2::size_report::SenderAdd() NEW +52 pw::async2::OnceSender<>::emplace<>() NEW +46 pw::async2::size_report::ReceiverTask<>::~ReceiverTask() NEW +44 pw::async2::OnceReceiver<>::~OnceReceiver() NEW +44 pw::async2::OnceSender<>::~OnceSender() NEW +44 pw::async2::size_report::ReceiverTask<>::ReceiverTask() NEW +40 _ZN2pw15internal_result12StatusOrDataIjLb1EEC2INS_6StatusETnNSt3__29enable_ifIXsr3std16is_constructibleIS4_OT_EE5valueEiE4typeELi0EEES8_ NEW +24 pw::async2::OnceReceiver<>::Pend()::{lambda()#1}::operator()() NEW +24 pw::async2::size_report::ReceiverTask<> NEW +22 pw::async2::size_report::ReceiverTask<>::DoPend() NEW +20 _ZNSt3__28optionalIN2pw6ResultIjEEEC2B8nn210000INS1_6StatusETnNS_9enable_ifIXclsr22_CheckOptionalLikeCtorIT_OS8_EE17__enable_implicitIS8_EEEiE4typeELi0EEEONS0_IS8_EE NEW +20 std::__2::pair<>::~pair() NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIjEELb0EE11__constructB8nn210000IJNS1_6StatusEEEEvDpOT_ NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIjEELb0EE16__construct_fromB8nn210000INS_8optionalINS1_6StatusEEEEEvOT_ NEW +12 _ZNRSt3__28optionalIjE5valueB8nn210000Ev NEW +12 _ZNSt3__227__throw_bad_optional_accessB8nn210000Ev NEW +6 std::__2::__libcpp_verbose_abort()	+960
	RAM NEW +8 pw::async2::sender_receiver_lock()::lock	+8
Cost of additional OnceSender / OnceReceiver template specialization	FLASH +88 pw::async2::size_report::Measure() +112 pw::async2::OnceReceiver<>::Pend() +96 pw::async2::OnceReceiver<>::OnceReceiver() +52 pw::async2::OnceSender<>::emplace<>() +46 pw::async2::size_report::ReceiverTask<>::~ReceiverTask() +44 pw::async2::OnceReceiver<>::~OnceReceiver() +44 pw::async2::OnceSender<>::~OnceSender() +44 pw::async2::size_report::ReceiverTask<>::ReceiverTask() +24 pw::async2::OnceReceiver<>::Pend()::{lambda()#1}::operator()() +24 pw::async2::size_report::ReceiverTask<> +22 pw::async2::size_report::ReceiverTask<>::DoPend() +18 std::__2::pair<>::~pair() +4 vClearInterruptMaskFromISR NEW +58 pw::async2::size_report::SenderSub() NEW +40 _ZN2pw15internal_result12StatusOrDataIiLb1EEC2INS_6StatusETnNSt3__29enable_ifIXsr3std16is_constructibleIS4_OT_EE5valueEiE4typeELi0EEES8_ NEW +20 _ZNSt3__28optionalIN2pw6ResultIiEEEC2B8nn210000INS1_6StatusETnNS_9enable_ifIXclsr22_CheckOptionalLikeCtorIT_OS8_EE17__enable_implicitIS8_EEEiE4typeELi0EEEONS0_IS8_EE NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIiEELb0EE11__constructB8nn210000IJNS1_6StatusEEEEvDpOT_ NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIiEELb0EE16__construct_fromB8nn210000INS_8optionalINS1_6StatusEEEEEvOT_ NEW +12 _ZNRSt3__28optionalIiE5valueB8nn210000Ev	+776