[Feature] KVCache: support multi-threading mode

[DwyaneShi]

Pull Request Description

L1 cache supports multi-threading.

Related Issues

Resolves: #[Insert issue number(s)]

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[gemini-code-assist]

Summary of Changes

Hello @DwyaneShi, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces multi-threading support for the L1 cache within the aibrix_kvcache system. The core change involves adding a configurable multi_threaded flag and implementing a ConditionalLock mechanism. This allows the L1 cache to be safely utilized in concurrent scenarios by protecting critical sections, while also offering the flexibility to disable locking overhead when operating in a single-threaded context.

Highlights

• Conditional Thread Safety: Introduced a new ConditionalLock utility that allows for thread-safe operations to be optionally enabled or disabled based on a configuration flag. This prevents unnecessary locking overhead in single-threaded environments while ensuring safety in multi-threaded ones.
• Multi-threading Configuration: Added a multi_threaded boolean flag to the KVCacheConfig to control whether the L1 cache should operate in a thread-safe manner.
• L1 Cache Thread Safety: Integrated the ConditionalLock into the L1 cache implementation, specifically protecting access to internal metadata, eviction policy operations, and cache block management (allocation, existence checks, puts, acquires, and deletes).

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[gemini-code-assist]

Code Review

This pull request introduces multi-threading support for the L1 cache by adding a ConditionalLock and using it to protect shared data structures. The overall approach is sound, but there are a few areas with potential race conditions and performance inefficiencies under concurrent access.

My review includes suggestions to:

• Correct a race condition in the metrics recording logic.
• Improve the efficiency of the allocation and eviction logic under contention.
• Reduce lock contention in the put operation.

Addressing these points will improve the robustness and performance of the multi-threaded cache.