perf: replaced Mutex with Spinlock in Dispatcher and Draw Pipeline

[mehah]

Description

This update replaces the use of mutex with spinlock in two critical parts of the system: the event dispatcher and the game draw pipeline. The change aims to optimize performance in multithreaded scenarios where critical sections are very short and accessed frequently.

📌 Technical Context

🧵 Event Dispatcher (Thread-local Buffers)

• Each thread maintains its own event buffer, avoiding contention during collection.
• At the end of the frame, all buffers are merged into a central structure.
• Previously, this merge process used a mutex, introducing OS-level overhead.
• It now uses a spinlock, allowing threads to wait without being suspended.

🎮 Draw Pipeline (Main Thread + Worker)

• The rendering system is split into:
  • Main thread: issues GPU draw commands.
  • Worker thread: gathers rendering data and sends it to the main thread.
• Synchronization between the two used to rely on mutex, now replaced with spinlock.
• As a result, a noticeable framerate improvement was observed due to reduced latency in the data exchange.

⚙️ Why Spinlock Instead of Mutex?

• mutex uses OS-level syscalls (e.g., futex) during contention, which can cause expensive context switches.
• spinlock avoids these syscalls by keeping the thread in a busy-wait loop, which is ideal when:
  • The critical section is very short.
  • The lock hold time is extremely low.
  • Operations are frequent and lightweight, such as in game loops and event merging.
• With spinlock, the synchronization cost drops from microseconds (mutex + syscall) to a few CPU cycles, improving:
  • Latency
  • Throughput
  • Framerate stability

🚀 Observed Results

• Significant reduction in lock contention latency.
• More stable framerate, with fewer micro-stutters during synchronization peaks.
• Lower jitter between event collection and frame rendering.

⚠️ Notes

• spinlock usage is carefully scoped to ultra-short critical sections to avoid excessive busy-waiting.
• Strategy will be revisited if contention levels increase in future versions.

[sonarqubecloud]

Quality Gate passed

Issues
12 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud