[LoRA] Lora shrink swizzle (#27694)

Signed-off-by: li2haipeng <44383182+li2haipeng@users.noreply.github.com>
Signed-off-by: Haipeng Li <li2haipeng@gmail.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>

Author: li2haipeng

vllm/lora/ops/triton_ops/lora_shrink_op.py

@@ -41,15 +41,24 @@ def _lora_shrink_kernel(
     BLOCK_K: tl.constexpr,
     EVEN_K: tl.constexpr,
     SPLIT_K: tl.constexpr,
+    GROUP_SIZE_M: tl.constexpr,
     SLICE_NUM: tl.constexpr,
 ):
     cta_n_num = tl.cdiv(N, BLOCK_N)
     cta_m_num = tl.cdiv(M, BLOCK_M)
 
     pid_sk_m_n = tl.program_id(axis=0)
     pid_sk = pid_sk_m_n % SPLIT_K
-    pid_m = (pid_sk_m_n // SPLIT_K) % cta_m_num
-    pid_n = pid_sk_m_n // (SPLIT_K * cta_m_num) % cta_n_num
+
+    pid_m_n = pid_sk_m_n // SPLIT_K
+    num_pid_in_group = GROUP_SIZE_M * cta_n_num
+    group_id = pid_m_n // num_pid_in_group
+    first_pid_m = group_id * GROUP_SIZE_M
+    group_size_m = min(cta_m_num - first_pid_m, GROUP_SIZE_M)
+
+    # Column-major ordering within groups for better cache reuse
+    pid_m = first_pid_m + ((pid_m_n % num_pid_in_group) % group_size_m)
+    pid_n = (pid_m_n % num_pid_in_group) // group_size_m
 
     slice_id = tl.program_id(axis=1)
     lora_idx = tl.program_id(axis=2)
@@ -194,6 +203,7 @@ def _lora_shrink(
     NUM_WARPS = kernel_config["num_warps"]
     NUM_STAGES = kernel_config["num_stages"]
     NUM_CTAS = kernel_config["num_ctas"]
+    GROUP_SIZE_M = kernel_config.get("group_size_m", 8)
     EVEN_K = K % (BLOCK_K * SPLIT_K) == 0  # type: ignore
 
     # TODO (varun): This grid formulation maximizes parallelization at the
@@ -233,6 +243,7 @@ def _lora_shrink(
         BLOCK_K,
         EVEN_K,
         SPLIT_K,
+        GROUP_SIZE_M,
         NUM_SLICES,
         num_warps=NUM_WARPS,
         num_ctas=NUM_CTAS,

vllm/lora/ops/triton_ops/utils.py

@@ -199,6 +199,7 @@ def get_lora_op_configs(
             "split_k": 64 if batch < 128 else 8,
             "num_warps": 4,
             "num_ctas": 1,
+            "group_size_m": 8,
             "num_stages": 2,
             "max_nreg": None,
         }