optimization qwen3-vl-4b TTFT for gfx1150 with 2 448x448 image and 256 text token input #1012
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qingxuamd wants to merge 2 commits into
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optimization qwen3-vl-4b TTFT for gfx1150 with 2 448x448 image and 256 text token input #1012qingxuamd wants to merge 2 commits into
qingxuamd wants to merge 2 commits into
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This optimization is for gfx1150. The model of Qwen3-VL-4B-Instruct-AWQ-4bit-lm_head_int8, for triton_w4a16_skinny_fmt_kernel, it cost more then 60% latency in prefill. The required input = 2 448x448 img + 256 token, then, tok num ~=660 tok. M: ~660 (2x448x448 + 256 token prefill） N,K（hot shape）： 660 x 19456 x 2560 660 x 2560 x 9728 660 x 6144 x 2560 660 x 2560 x 4096 warps, currently 8 is best num so: BLOCK_M=64 BLOCK_N=256 BLOCK_K=32 num_warps=8 GEMM：M=671，N/K as above kernel tile：64,256,32,8 Signed-off-by: Xu Qing <qing.xu2@amd.com>
Add a Qwen3-VL-4B prefill shape guard in Triton unified attention on gfx11 and apply BM64/T32/W4/S1/EU4 defaults to reduce TTFT. Also fix prefill tile override wiring so VLLM_UA_PREFILL_TILE_SIZE is honored instead of being overwritten by the default path. Signed-off-by: Xu Qing <qing.xu2@amd.com>
mgehre-amd
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Jun 22, 2026
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| # Profile-guided default for Qwen3-VL-like multimodal prefill. | ||
| qwen3_prefill_shapes = { | ||
| (19456, 2560), # gate_up_proj-like | ||
| (2560, 9728), # down_proj-like | ||
| (6144, 2560), # qkv_proj-like | ||
| (2560, 4096), # o_proj-like | ||
| } | ||
| if 576 <= M <= 832 and (N, K) in qwen3_prefill_shapes: | ||
| return 64, 256, min(32, group_size), 8 | ||
|
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This change already landed in https://github.com/ROCm/vllm/pull/1009/changes for bfloat16.
Could you please put this in the same shape, i.e.
if on_gfx1103() and M > 256:
# Tested on Qwen3-VL-4B-AWQ
block_m, block_n, block_k, num_warps = 64, 256, 64, 8
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Specifically optimize the kernel tile according to qwen3-vl-4b and input shape, without this PR, TTFT=1231 ms, with this PR, TTFT = 980 ms.