[Core] Use KVCacheBlock as much as possible instead of dict[block_id, KVCacheBlock] #24830
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heheda12345
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Sep 14, 2025
Currently away from keyboard, thanks for your reviews. Will address them later in the day. The metrics are distributions of GC elapsed time. And will provide more data for e2e speedup. |
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Done. Added more metric descriptions in the summary and also added e2e speedup measurements. |
njhill
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Sep 15, 2025
heheda12345
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Sep 16, 2025
njhill
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Sep 16, 2025
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Resolve #24321 |
njhill
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Sep 16, 2025
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Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
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Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
heheda12345
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… KVCacheBlock] (vllm-project#24830) Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
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… KVCacheBlock] (#24830) Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com> Signed-off-by: yewentao256 <zhyanwentao@126.com>
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Purpose
dict[block_id, KVCacheBlock] is the currently the top GC objects, however, most of the time, each BlockHashWithGroupId simply map to a single KVCacheBlock. So we replace dict[block_id, KVCacheBlock] with Union[KVCacheBlock, dict[block_id, KVCacheBlock]] in block cache, and use KVCacheBlock as much as possible to reduce the GC overhead.
Test Plan & Test Result
Patch #24829 locally with a breakdown analysis, we could see that the GC cost is left shifted as expected.
E2E Metrics
Model: facebook/opt-125m
Prefill-heavy work: prefill 2000 decode 48
Decode-heavy work: prefill 48 decode 2000
max-concurrency:
|Request-Rate|Before|After|
|Prefill-heavy|212.98|217.40 (+2%)|
|Decode-heavy|13.89|14.10 (+1.5%)|
facebook/opt-125m decode heavy workload: prefill 48 decode 2000
GC cost reduced by 17% (per histogram of GC elapsed time)
Essential Elements of an Effective PR Description Checklist
supported_models.mdandexamplesfor a new model.