MalikHou opened a new pull request, #3238:
URL: https://github.com/apache/brpc/pull/3238
Event Dispatcher Unsched Flag
### What problem does this PR solve?
Problem Summary:
- Event-dispatch scheduling behavior was not unified across transports.
- RDMA used a transport-specific flag (`rdma_edisp_unsched`), while TCP had
no unified switch.
- In RDMA path, `bthread_start_urgent` and `bthread_start_background` logic
was reversed, causing behavior opposite to expected unsched semantics.
- The scheduling decision logic was duplicated in transport code, making
behavior harder to reason about and test.
### What is changed and the side effects?
Changed:
- Added a unified flag in dispatcher layer: `event_dispatcher_edisp_unsched`.
- Added `EventDispatcherUnsched()` helper in `event_dispatcher.{h,cpp}` as
single source of truth.
- Updated `TcpTransport::ProcessEvent` and `RdmaTransport::ProcessEvent` to
use `EventDispatcherUnsched()`:
- `false` -> `bthread_start_urgent`
- `true` -> `bthread_start_background`
- Fixed RDMA bug where `bthread_start_urgent` and `bthread_start_background`
branches were previously swapped.
- Deprecated `rdma_edisp_unsched` and kept compatibility through
dispatcher-layer unified check.
- Added/updated tests in `test/brpc_event_dispatcher_unittest.cpp`:
- `event_dispatcher_unsched_by_unified_flag`
- `event_dispatcher_unsched_by_legacy_rdma_flag` (when `BRPC_WITH_RDMA`)
- `tcp_unsched_true_returns_before_onedge_finish`
- `tcp_unsched_false_blocks_caller_when_single_worker`
Effects:
- `event_dispatcher_edisp_unsched=true` may reduce immediate foreground
switching of dispatcher path.
- `rdma_edisp_unsched` is deprecated.
- RDMA runtime behavior now matches intended unsched semantics after
fixing the swapped urgent/background branches. Users depending on previous
incorrect behavior should migrate and re-check tuning.
---
### Check List:
- [x] Please make sure your changes are compilable.
- [x] When providing us with a new feature, it is best to add related tests.
- [x] Please follow [Contributor Covenant Code of
Conduct](https://github.com/apache/brpc/blob/master/CODE_OF_CONDUCT.md).
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