⚡ Bolt: pass std::string by const reference to avoid unnecessary copies in RDMA ops

[google-labs-jules]

💡 What: Modified post_block_send, execute_rdma_writes, and prepare_write_requests in RDMACommunicator to take data_type as const std::string& instead of const std::string. Added inline comments explaining the performance optimization.
🎯 Why: Passing strings by value incurs a heap allocation and copy on every call. In high-frequency RDMA caching operations, this adds unnecessary overhead. Passing by const reference avoids the copy.
📊 Impact: Reduces memory allocations and slightly decreases CPU overhead in the critical path for cache operations.
🔬 Measurement: Verify by checking that no string copies occur for the data_type argument during function invocations in profiling traces for post_block_send.

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PR created automatically by Jules for task 10329764267201400303 started by @ZeyuChen

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[fastdeploy-bot]

🤖 AI Code Review | 2026-04-08 10:35 CST

📋 Review 摘要

PR 概述：将 RDMA 通信中的 data_type 参数从按值传递改为引用传递，避免不必要的字符串拷贝，提升性能。

变更范围：fastdeploy/cache_manager/transfer_factory/kvcache_transfer/（核心逻辑）、custom_ops/gpu_ops/（格式化变更）

影响面 Tag：[Optimization] [KVCache]

📝 PR 规范检查

问题：PR 标题缺少官方要求的 Tag。

标题建议（可直接复制）：

• [Optimization] Bolt: pass std::string by const reference to avoid unnecessary copies in RDMA ops
• [KVCache] Bolt: pass std::string by const reference to avoid unnecessary copies in RDMA ops

可接受的官方 Tag：[Optimization]、[KVCache]

问题

级别	文件	概述
🔴 兼容性	PR 标题	缺少官方 Tag，不符合 PR 规范

总体评价

核心代码变更正确：将 data_type 参数从 const std::string 改为 const std::string& 可以避免不必要的字符串拷贝，在高频 RDMA 缓存操作场景下有性能收益。调用方传递字符串字面量（如 "key"、"value"），隐式转换兼容。但 PR 标题不符合规范，需要添加官方 Tag。

[fastdeploy-bot]

🔴 兼容性 PR 标题缺少官方要求的 Tag。

根据 FastDeploy PR 规范，标题必须包含官方 Tag 之一，如 [Optimization]、[KVCache]、[Feature] 等。

建议修改标题为：

• [Optimization] Bolt: pass std::string by const reference to avoid unnecessary copies in RDMA ops

或者：

• [KVCache] Bolt: pass std::string by const reference to avoid unnecessary copies in RDMA ops