[Core] Don't count preempted tokens in prefix cache hit rate #25787
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Signed-off-by: Zhuohan Li <[email protected]>
zhuohan123
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Code Review
This pull request correctly modifies the prefix cache hit rate calculation to exclude tokens from preempted requests. The changes are implemented by adding a preemption counter to requests, which is then used to separate statistics for new and preempted requests. The implementation is clean and directly addresses the issue. The associated refactoring in the scheduler improves code readability. I have reviewed the changes and found no issues.
zhuohan123
commented
Sep 26, 2025
| self.encoder_cache_manager.free(preempted_req) | ||
| preempted_req.status = RequestStatus.PREEMPTED | ||
| preempted_req.num_computed_tokens = 0 | ||
| preempted_req.num_preemptions += 1 |
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Note: this line is the only actual change in this file, all other changes are code style change.
WoosukKwon
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Sep 26, 2025
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LGTM. Thanks for doing this.
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Purpose
Do not count preempted tokens in prefix cache hit rate. See #25780 for details.
Test
Existing test should pass, and now when we run:
We see
Prefix cache hit ratedroped from 30% to 0.2%.Essential Elements of an Effective PR Description Checklist
supported_models.mdandexamplesfor a new model.