chenBright opened a new pull request, #3700:
URL: https://github.com/apache/brpc/pull/3700
### What problem does this PR solve?
Issue Number: resolve
Problem Summary:
`Agent::merge_global()` creates a temporary `shared_ptr` through the
conditional expression
` c ? c : combiner.lock()`, even though its result is bound to a const
reference. This adds
reference-count updates to every normal percentile write and causes
contention when multiple
threads update the same `LatencyRecorder`.
### What is changed and the side effects?
Changed:
- Accept the supplied owner by const reference and use separate branches to
avoid copying it.
- Preserve ownership through `weak_ptr::lock()` when no owner is supplied,
and skip the operation
if the combiner has expired.
Side effects:
- Performance effects: Removes redundant reference-count updates from the
normal percentile write path.
- Breaking backward compatibility: None.
Local benchmark results for writers sharing one LatencyRecorder:
| Writers | Before (ns/op) | After (ns/op) | Reduction |
|---|---:|---:|---:|
| 1 | 59.1 | 46.8 | 20.9% |
| 8 | 158.1 | 19.9 | 87.4% |
---
### 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](https://github.com/apache/brpc/blob/master/CODE_OF_CONDUCT.md).
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