[KV offload] Parallel-agnostic fs-tier cache for single full-attention group#44733
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orozery merged 9 commits intoJun 11, 2026
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…n group Enable parallel_agnostic=True only for a single full-attention KV-cache group so the fs-tier offload cache can be reused across tensor/pipeline parallel sizes. Signed-off-by: Itay Etelis <itay.etelis@ibm.com>
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orozery
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Jun 8, 2026
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| # A single full-attention group has a parallelism-invariant offloaded | ||
| # block, so share its cache across parallel sizes. Replicated KV (MLA, | ||
| # small-GQA) is world_size-scaled and fails closed on the load size check. | ||
| kv_cache_groups = offloading_spec.kv_cache_config.kv_cache_groups | ||
| parallel_agnostic = len(kv_cache_groups) == 1 and isinstance( | ||
| kv_cache_groups[0].kv_cache_spec, FullAttentionSpec | ||
| ) |
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Let's move this logic inside the FileMapper (so other tiers can "enjoy" it as well).
And set parallel_agnostic=True here (and in the obj tier as well)
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You're right,
sorry about that.
Tiers opt in with parallel_agnostic=True; FileMapper gates it on a single full-attention group. Signed-off-by: Itay Etelis <itay.etelis@ibm.com>
orozery
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Jun 9, 2026
MLA latent KV is replicated per rank, never head-sharded. Signed-off-by: Itay Etelis <itay.etelis@ibm.com>
Signed-off-by: Itay Etelis <itay.etelis@ibm.com>
orozery
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Jun 10, 2026
Signed-off-by: Itay Etelis <itay.etelis@ibm.com>
orozery
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Jun 11, 2026
ryttry
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Jun 11, 2026
…n group (vllm-project#44733) Signed-off-by: Itay Etelis <itay.etelis@ibm.com> Co-authored-by: Itay Etelis <itay.etelis@ibm.com>
Saddss
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Jun 14, 2026
…n group (vllm-project#44733) Signed-off-by: Itay Etelis <itay.etelis@ibm.com> Co-authored-by: Itay Etelis <itay.etelis@ibm.com>
Etelis
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Jun 18, 2026
The parallel-agnostic fs-tier cache (vllm-project#44733) collapses tp/pp/pcp/dcp and rank out of the cache namespace for a single full-attention group, on the assumption that the offloaded KV blocks are parallelism-invariant. That invariant is not known to hold under the V2 model runner, whose KV layout may differ, so sharing a cache directory across layouts there could alias distinct blocks. Gate the opt-in on the canonical vllm_config.use_v2_model_runner property (not a raw env-var read, so config-driven V2 defaults such as diffusion models are handled correctly). The check sits alongside the existing MLA and multi-group exclusions in FileMapper, keeping the call sites unchanged. Adds a regression test asserting tp/rank are not collapsed when the V2 model runner is active. Co-authored-by: Claude Signed-off-by: Itay Etelis <etelis2019@gmail.com>
Etelis
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Jun 18, 2026
The parallel-agnostic fs-tier cache (vllm-project#44733) collapses tp/pp/pcp/dcp and rank out of the cache namespace for a single full-attention group, assuming the offloaded blocks are parallelism-invariant. That assumption is not known to hold under the V2 model runner, so gate the opt-in on vllm_config.use_v2_model_runner alongside the existing MLA and multi-group exclusions. Signed-off-by: Itay Etelis <etelis2019@gmail.com>
divineearthly
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…n group (vllm-project#44733) Signed-off-by: Itay Etelis <itay.etelis@ibm.com> Co-authored-by: Itay Etelis <itay.etelis@ibm.com> Signed-off-by: divineearthly <divineearthly@gmail.com>
tunglinwood
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Jun 22, 2026
…n group (vllm-project#44733) Signed-off-by: Itay Etelis <itay.etelis@ibm.com> Co-authored-by: Itay Etelis <itay.etelis@ibm.com>
nkzhenhua
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Jun 24, 2026
…n group (vllm-project#44733) Signed-off-by: Itay Etelis <itay.etelis@ibm.com> Co-authored-by: Itay Etelis <itay.etelis@ibm.com>
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Tests
pytest tests/v1/kv_offload/tiering/test_fs_tier.py— adds 3 predicate cases (single full-attn →agnostic; multi-group → off; non-full-attn → off).
Validated end-to-end on 4×H100 (store TP=2 → load TP=4, same cache dir):
Short read→ recompute → correct outputShort read→ recompute → correct output