[webgpu] Fused SplitPackedQKV with FusedQKRotaryEmbedding - #26447
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Xiaofei Han (xiaofeihan1) merged 5 commits intoNov 11, 2025
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Jiajia Qin (qjia7)
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Guenther Schmuelling (guschmue)
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Xiaofei Han (xiaofeihan1)
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…26447) ### Description <!-- Describe your changes. --> When `is_packed_qkv_` and `do_rotary_`, call a new `SplitPackedQKVWithRotaryEmbedding` which fused SplitPackedQKV with FusedQKRotaryEmbedding. Dispatch size is B*S*N*work_per_head. (work_per_head is `head_size - half_rotary_embedding_dim`, is equal `half_rotary_embedding_dim + need_copy_dim`) - For `half_rotary_embedding_dim`, we split packedQKV and then do rotary for pairs q/k and directly store v. - For `need_copy_dim`, we split packedQKV and then directly store q/k/v ### Motivation and Context On NV5080, the token generation speed improve ~3%. | generation tps | Before | After | |--------|--------|-------| | NV5080 | 129 | **133** | | Intel | 15.4 | 15.5 | | Mac | 69.0 | 71.0 |
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Description
When
is_packed_qkv_anddo_rotary_, call a newSplitPackedQKVWithRotaryEmbeddingwhich fused SplitPackedQKV with FusedQKRotaryEmbedding.Dispatch size is BSN*work_per_head. (work_per_head is
head_size - half_rotary_embedding_dim, is equalhalf_rotary_embedding_dim + need_copy_dim)half_rotary_embedding_dim, we split packedQKV and then do rotary for pairs q/k and directly store v.need_copy_dim, we split packedQKV and then directly store q/k/vMotivation and Context
On NV5080, the token generation speed improve ~3%.