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Documentation preview: https://vllm--61175.org.readthedocs.build/en/61175/ |
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| # This is a per-GET limit, not a reservation across concurrent receivers. | ||
| self.disk_offload_buffer_budget_bytes: int | None = None | ||
| if store_config.enable_dfs: | ||
| self.disk_offload_buffer_budget_bytes = store_config.local_buffer_size |
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With enable_offload and enable_dfs both on, this limit becomes local_buffer_size. But Mooncake reads the LOCAL_DISK (SSD) replica before the DFS replica, and the SSD owner buffer is only 1280 MB. So a load over 1280 MB now fails with BUFFER_OVERFLOW. Before, it was split to fit.
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Good catch, thanks. I reproduced it on 3FS with standalone-store, enable_offload + enable_dfs and local_buffer_size=2GB: with the memory replicas evicted, a 30k-token prompt (~1.7 GB of KV) went out as one GET of 1874 keys, the owner returned BUFFER_OVERFLOW and the request failed. With both flags on, the budget is now min(local_buffer_size, 1280 MB), so the same load is split into two GETs, all keys load, and the output matches. Added a unit test and a line in the docs.
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Would appreciate your review on this Mooncake DFS support PR. The upstream Mooncake dependency has also been merged. Thanks! |
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This pull request has merge conflicts that must be resolved before it can be |
Add an opt-in "enable_dfs" option to the Mooncake JSON config. When set, the connector initializes Mooncake's DFS backend during Store setup and writes one DFS replica per object plus replica_num memory replicas (kv_connector_extra_config, default 1). replica_num=0 stores objects only in DFS and requires kvcache-ai/Mooncake#4637. DFS is limited to the default tenant and is rejected for the cross-encoder cache. DFS loads are split so each GET fits in local_buffer_size, or in the SSD owner's staging buffer if smaller when enable_offload is also set, since Mooncake reads SSD replicas first. Tested with the Mooncake store unit tests and a 3FS run on Mooncake main (d855a6ae) with replica_num 0 and 1. Co-authored-by: Claude <noreply@anthropic.com> Signed-off-by: Daegyu Han <daegyu94.han@samsung.com>
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Overview
Add an opt-in Mooncake DFS tier (e.g. 3FS) to
MooncakeStoreConnector, so stored KV can live in a shared file system instead of, or in addition to, host memory. Builds on #42689.Claims
"enable_dfs": truein the Mooncake config writes one DFS replica per object plusreplica_nummemory replicas (kv_connector_extra_config, default 1).replica_num: 0stores KV only in DFS (requires [Store] Allow DFS-only replica placement kvcache-ai/Mooncake#4637).replica_numwithout DFS) fail at startup.Validation
d855a6ae, Qwen2.5-0.5B-Instruct, single GPU: generate, reset the local prefix cache, generate again.replica_numDetails
enable_dfslives in the Mooncake JSON with othersetup()-time options (enable_offload,tenant_id);replica_numlives inkv_connector_extra_configwith other per-put options (preferred_segment). Setup steps are in the usage guide's "DFS Tier" section.replica_num: 0needs an unreleased Mooncake Master; one load receive thread, since concurrent GETs share the client buffer (a warning is logged otherwise); validated on a single node inembeddedmode and instandalone-storemode withenable_offload. CI cannot run the DFS path because it needs 3FS.Pull Request Checklist
I used vLLM's
/pr-checklistskill. (Mandatory for agents, optional for humans).AI assistance was used during the creation of this PR.
Design Fit: Minimizes impact on core components, reuses existing functionality, and justifies added complexity.
Testing and Validation: Validates the change and ensures any added tests are meaningful and reliable, with CI coverage or documented CI resource constraints and validation performed outside CI.
Code Quality and Style: Keeps code and comments clear and concise, and updates relevant documentation and examples.
Pull Request Contents: Includes a brief summary and relevant links, supports claims with evidence, explains root causes and implementation trade-offs, and follows the contributing guide.