GIC vs Event-Driven Architecture: Analysis
1. Essential Similarities
Yes, fundamentally consistent. Both implement the same core pattern: decoupled event routing.
Aspect | GIC | Reactor/Actor |
Event Source | Hardware peripherals (IRQ lines) | I/O events, messages |
Dispatcher | Distributor → CPU interface | Event loop / Scheduler |
Handler | ISR (Interrupt Service Routine) | Callback / Actor mailbox |
Routing Logic | Affinity, priority, grouping | Selector, dispatcher rules |
Shared principles:
- Multiplexing: Many sources → single dispatcher → multiple handlers
- Priority arbitration: Higher priority events preempt lower ones
- Asynchronous decoupling: Producer doesn't block waiting for consumer
- Handler isolation: Each handler runs independently
2. Key Differences
Dimension | GIC (Hardware) | Event-Driven (Software) |
Preemption | True preemption via CPU exception | Cooperative (reactor) or OS-scheduled (actor) |
Latency | Deterministic, sub-microsecond | Variable, depends on event loop/scheduler |
State Model | Stateless dispatch; state in peripheral/memory | Stateful actors with encapsulated mailboxes |
Concurrency | Physical parallelism (multi-core) | Logical concurrency (single-threaded reactor) or physical (actor systems) |
Failure Isolation | Fault may crash entire system | Actor supervision trees enable fault recovery |
Routing Granularity | Fixed IRQ number → CPU affinity bitmap | Dynamic routing rules, content-based dispatch |
Critical distinction:
GIC operates at hardware abstraction level — it's a mechanism, not a model. Event-driven architectures are programming models built atop such mechanisms.
GIC is the foundation layer that enables efficient event-driven software. Reactor/Actor patterns are higher-level abstractions that organize application logic.
Summary
Question | Answer |
Essentially similar? | Yes — same dispatch pattern |
Interchangeable? | No — different abstraction layers |
Relationship | GIC enables efficient software event loops |
The GIC can be viewed as a hardware reactor — single-purpose, zero-overhead, but inflexible. Software patterns trade latency for flexibility, fault tolerance, and programmability.
Mailbox vs Pub/Sub
No. Mailbox is point-to-point; Pub/Sub is broadcast.
Core Distinction
Aspect | Mailbox (Actor) | Pub/Sub |
Addressing | Direct: sender → specific actor | Indirect: publisher → topic → subscribers |
Cardinality | 1:1 (one sender, one receiver) | 1:N (one publisher, many subscribers) |
Coupling | Sender knows receiver identity | Publisher unaware of subscribers |
Message Fate | Consumed once by owner | Copied to all subscribers |
Backpressure | Per-actor queue depth | Per-subscriber or topic-level |
Mental Model
When They Converge
- Single subscriber pub/sub degrades to mailbox-like behavior
- Actor with broadcast can simulate pub/sub (fan-out pattern)
- Both are asynchronous and decoupled in time
Key Tradeoff
Model | Strength | Weakness |
Mailbox | Precise routing, natural backpressure | Must know recipient |
Pub/Sub | Full decoupling, dynamic subscribers | No delivery guarantee per-subscriber |
Summary: Mailbox = addressed envelope. Pub/Sub = bulletin board.
Mailbox vs Pub/Sub
No. Mailbox is point-to-point; Pub/Sub is broadcast.
Core Distinction
Aspect | Mailbox (Actor) | Pub/Sub |
Addressing | Direct: sender → specific actor | Indirect: publisher → topic → subscribers |
Cardinality | 1:1 (one sender, one receiver) | 1:N (one publisher, many subscribers) |
Coupling | Sender knows receiver identity | Publisher unaware of subscribers |
Message Fate | Consumed once by owner | Copied to all subscribers |
Backpressure | Per-actor queue depth | Per-subscriber or topic-level |
Mental Model
When They Converge
- Single subscriber pub/sub degrades to mailbox-like behavior
- Actor with broadcast can simulate pub/sub (fan-out pattern)
- Both are asynchronous and decoupled in time
Key Tradeoff
Model | Strength | Weakness |
Mailbox | Precise routing, natural backpressure | Must know recipient |
Pub/Sub | Full decoupling, dynamic subscribers | No delivery guarantee per-subscriber |
Summary: Mailbox = addressed envelope. Pub/Sub = bulletin board.
