I/O Objects T H E N E T W O R K I N G T S F R O M S C R A T C H Robert Leahy - rleahy@rleahy.caNetworking TS & Asio ISO C++ Networking is blocked on Executors (P0443) Target for Networking is composed asynchronous operations depend on those guarantees being honored transitively 6I/O Objects “I/O objects” provide a handle to low level asynchronous functionality within the framework of the Networking one or more I/O objects) is a useful pattern 19Service Named Type Requirement Service objects own completion handlers thereby breaking the potential ownership cycle Service objects are owned by an

std::string Bar std::stringObject Introspection (OI) Goals • Byte level memory footprint analysis for objects • Complete object type hierarchies • Dynamic allocations and containers • Optimised, production void doit(Foo&, Foo&) ‘this’ pointer entry:_ZN3FooD1Ev:this // Foo::~Foo() Global data global:myGlobalState Probe examples1. Inject OI into the target process 2. Wait for a thread to (Cumulative) Feature folly::small_vector 414132 8 2.359 10 0 88 25315061 • 2800 nested objects of type ‘FooBar’ were analysed. Top of the list: • UnusedSz (cumulative) = (10 - 2.359) * 8 * 4141321

pointers protect access to objects that may be removed concurrently. SAFE RECLAMATION Concurrency TS2 Essential Hazard Pointer Interface Base class for protectable objects template class time) Asynchronous Reclamation • Asynchronous reclamation is invoked when the number of retired objects reaches some threshold: • In the Folly library: • The threshold is the max of 1000 and twice the Extract retired objects from lists in the (global) domain structure. • Read hazard pointer values • Match addresses of retired objects with values read from hazard pointers. • Push matched objects back into

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10 Scope of Variables 105 10.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 10.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 164 12.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 12.10 Empty generic functions 3 Data Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 25.4 Global variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 25.5 Parallel

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10 Scope of Variables 105 10.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 10.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 164 12.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 12.10 Empty generic functions 3 Data Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 25.4 Global variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 25.5 Parallel

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 11 Scope of Variables 111 11.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 11.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 173 13.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.10 Empty generic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.7 Constructors are just callable objects . . . . . . . . . . . . . . . . . . . . . . . . . 190 15 Conversion and Promotion 192 15.1 Conversion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 11 Scope of Variables 111 11.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 11.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 173 13.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.10 Empty generic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.7 Constructors are just callable objects . . . . . . . . . . . . . . . . . . . . . . . . . 190 15 Conversion and Promotion 192 15.1 Conversion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 11 Scope of Variables 111 11.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 11.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 173 13.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.10 Empty generic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.7 Constructors are just callable objects . . . . . . . . . . . . . . . . . . . . . . . . . 190 15 Conversion and Promotion 192 15.1 Conversion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 11 Scope of Variables 111 11.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 11.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 173 13.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.10 Empty generic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.7 Constructors are just callable objects . . . . . . . . . . . . . . . . . . . . . . . . . 190 15 Conversion and Promotion 192 15.1 Conversion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 11 Scope of Variables 111 11.1 Global Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 11.2 Local Optional and keyword Arguments . . . . . . . . . . . . . . . . . . . . . . . 173 13.9 Function-like objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.10 Empty generic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.7 Constructors are just callable objects . . . . . . . . . . . . . . . . . . . . . . . . . 190 15 Conversion and Promotion 192 15.1 Conversion