[Perf] Optimize batch invariant BMM, 18.1% Throughput improvement, 10.7% TTFT improvement (#29345)

Signed-off-by: yewentao256 <zhyanwentao@126.com>
Signed-off-by: Wentao Ye <44945378+yewentao256@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

tests/v1/determinism/utils.py

@@ -8,6 +8,7 @@ import torch
 
 from vllm.attention.utils.fa_utils import flash_attn_supports_mla
 from vllm.platforms import current_platform
+from vllm.utils.flashinfer import has_flashinfer
 
 skip_unsupported = pytest.mark.skipif(
     not (current_platform.is_cuda() and current_platform.has_device_capability(90)),
@@ -16,9 +17,11 @@ skip_unsupported = pytest.mark.skipif(
 
 BACKENDS: list[str] = [
     "FLASH_ATTN",
-    "FLASHINFER",
 ]
 
+if has_flashinfer():
+    BACKENDS.append("FLASHINFER")
+
 if flash_attn_supports_mla():
     BACKENDS.append("FLASH_ATTN_MLA")