Support dynamic expansion of RDMA block pool

[chenBright]

What problem does this PR solve?

Issue Number:

Problem Summary:

When FLAGS_rdma_memory_pool_buckets > 1, the block pool cannot be dynamically expanded.

What is changed and the side effects?

Changed:

Dynamically expanded memory is stored in an expansion_list protected by extend_lock, and each bucket only retrieves memory from the expansion_list at the corresponding index.

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[Copilot]

Pull Request Overview

This PR enhances the RDMA block pool to support dynamic memory expansion when multiple buckets are configured. Previously, dynamic expansion was restricted when FLAGS_rdma_memory_pool_buckets > 1, limiting scalability.

Key Changes:

• Introduces expansion_list and expansion_size arrays to stage newly allocated memory before distributing it to buckets
• Removes the restriction preventing dynamic expansion with multiple buckets
• Refactors memory management to use scope guards for cleaner lock handling
• Deprecates FLAGS_rdma_memory_pool_user_specified_memory flag while maintaining backward compatibility

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
src/butil/memory/scope_guard.h	Adds BUTIL_SCOPE_EXIT macro as an alias to BRPC_SCOPE_EXIT for consistent naming across the codebase
src/brpc/rdma/block_pool.cpp	Implements expansion_list mechanism for thread-safe dynamic memory expansion, refactors lock management using scope guards, and updates memory pool extension logic

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[yanglimingcn]

When FLAGS_rdma_memory_pool_buckets is greater than 1, a bug may occur due to lock granularity issues.

[chenBright]

When FLAGS_rdma_memory_pool_buckets is greater than 1, a bug may occur due to lock granularity issues.

This PR can solve this problem.

[yanglimingcn]

FLAGS_rdma_memory_pool_user_specified_memory is used to allow users to register specific memory, such as SPDK. In these scenarios, memory needs to be allocated by SPDK and then registered in RDMA, which can achieve zero copy.

[chenBright]

FLAGS_rdma_memory_pool_user_specified_memory is used to allow users to register specific memory, such as SPDK. In these scenarios, memory needs to be allocated by SPDK and then registered in RDMA, which can achieve zero copy.

Ok, I will revert it.

When the idle_list is out of memory in AllocBlockFrom function, it seems that the user cannot immediately dynamically expand specific memory. Is that right?

[yanglimingcn]

In this scenario, the memory should be pre-registered, and dynamic allocation requires the user to provide memory too.

[chenBright]

FLAGS_rdma_memory_pool_user_specified_memory is used to allow users to register specific memory, such as SPDK. In these scenarios, memory needs to be allocated by SPDK and then registered in RDMA, which can achieve zero copy.

Ok, I will revert it.

@yanglimingcn done

[yanglimingcn]

LGTM

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 10 comments.

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