Performance

This page documents the performance optimizations employed by NamedSignal.

What We Optimize For

Unlike many libraries that boast to be "the fastest signal library", we don't make ergonomical sacrifices or use-case assumptions. That is, we attempt to balance for every possible scenario, ranging from single-digit to thousands of connections, non-yielding and yielding listeners, and more.

We avoid micro-optimizations that hurt ergonomics. No array-based API and indexing a number to check connection status, no FireSync/Async/Unsafe, and no caveats.

Optimizations

Minimized Resumption for Non-Yielding Connections

Most signal libraries cache one or more threads, however there is still a very large overhead for resumption.

We improve upon this by using a more efficient dispatching technique that only resumes more threads when a callback yields, leading to vastly better non-yielding invocation performance with multiple connections.

Multi Thread Recycling

Every thread created for invocation is reused whenever possible, cutting down the significant overhead for churning threads.

Dual Layer Thread Cache

We implement 2 layers of thread caching, a 'fast' L1 cache (a local variable), and a slower L2 cache (an array).

Accessing an upvalue is faster than indexing or inserting into an array, thus slighting improving performance for light, repetitive, and non-yielding invocations.

Linked Lists for O(1) Disconnect

Connections use doubly linked lists to maintain order while allowing constant-time disconnections.

While they are slower to iterate than an array, they avoid the extremely expensive shifting required by arrays when disconnecting.

Avoiding The OOP API Internally

When a function that is part of the OOP interface is depended on internally, it's instead defined as a const function, which skips the __index lookup and allows the Luau compiler to perform function inling.

Benchmarks

Benchmarks are a work in progress!

For now testing uses Gohan's Certification's Speed Certification:

⚪ | Speed Certification     |  -  Server - Signal_Certifications:2023
--------------------------------------------------------------------------------------  -  Server - Signal_Certifications:1968
☑ | Create         | -0.5μs  | Baseline: 0.6μs  ▶ {...} | Results: 0.1μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Connect        | -0.6μs  | Baseline: 0.8μs  ▶ {...} | Results: 0.2μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Once           | -0.4μs  | Baseline: 0.7μs  ▶ {...} | Results: 0.2μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Fire_None      | -0.0μs  | Baseline: 0.1μs  ▶ {...} | Results: 0.1μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Fire_One       | +0.3μs  | Baseline: 0.4μs  ▶ {...} | Results: 0.6μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Fire_Many      | -0.1μs  | Baseline: 0.1μs  ▶ {...} | Results: 0.0μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Fire_OneYield  | +0.2μs  | Baseline: 0.6μs  ▶ {...} | Results: 0.9μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Fire_ManyYield | +0.5μs  | Baseline: 0.1μs  ▶ {...} | Results: 0.6μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | Disconnect     | -0.1μs  | Baseline: 0.2μs  ▶ {...} | Results: 0.1μs  ▶ {...}  -  Server - Signal_Certifications:225
☑ | DisconnectAll  | -6.0μs  | Baseline: 7.2μs  ▶ {...} | Results: 1.2μs  ▶ {...}  -  Server - Signal_Certifications:225
--------------------------------------------------------------------------------------  -  Server - Signal_Certifications:1968
✅ | Speed Certified         |  -  Server - Signal_Certifications:125