fix(kv-offload): don't CP-scale tokens_per_block for replicated groups - #10
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build_offloading_config() multiplied every group's block size by the context-parallel factor unconditionally. That was correct when all KV cache groups were CP-sharded, but dcp_replicated groups keep the full cache on every rank, so one of their blocks covers exactly block_size global tokens -- which is why SingleTypeKVCacheManager.__init__ excludes them from the same scaling. The connector therefore saw G * cp where the manager uses G. Since num_gpu_blocks, tokens_per_chunk and hashes_per_chunk all derive from tokens_per_block, the affected group's block and chunk counts came out a factor of cp too small and its offload keys landed on the wrong token boundaries, silently corrupting that group's KV on a load hit. Mirror the manager's rule so both agree on the effective block size. Affects any cp > 1 run combining the offloading connector with a replicated group: DFlash draft groups, the DeepSeek V3.2 sparse indexer, and the DeepSeek V4 compressor. Signed-off-by: Procr <193802945+procr1337@users.noreply.github.com>
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added to #9 |
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build_offloading_config() multiplied every group's block size by the context-parallel factor unconditionally. That was correct when all KV cache groups were CP-sharded, but dcp_replicated groups keep the full cache on every rank, so one of their blocks covers exactly block_size global tokens -- which is why SingleTypeKVCacheManager.init excludes them from the same scaling.
The connector therefore saw G * cp where the manager uses G. Since num_gpu_blocks, tokens_per_chunk and hashes_per_chunk all derive from tokens_per_block, the affected group's block and chunk counts came out a factor of cp too small and its offload keys landed on the wrong token boundaries, silently corrupting that group's KV on a load hit.
Mirror the manager's rule so both agree on the effective block size. Affects any cp > 1 run combining the offloading connector with a replicated group: DFlash draft groups, the DeepSeek V3.2 sparse indexer, and the DeepSeek V4 compressor.