Fuse sorted_token_ids padding to moe_align_block_size kernel (#7437)

sgl-kernel/benchmark/bench_moe_align_block_size.py

@@ -5,7 +5,11 @@ import torch
 import triton
 import triton.language as tl
 from sgl_kernel import moe_align_block_size as sgl_moe_align_block_size
-from vllm import _custom_ops as ops
+
+try:
+    from vllm import _custom_ops as ops
+except ImportError:
+    ops = None
 
 USE_RANDOM_PERM = False
 
@@ -208,7 +212,7 @@ def calculate_diff(num_tokens, num_experts=256, block_size=128, topk=8):
         )
         print(f"✅ VLLM implementation works with {num_experts} experts!")
         vllm_works = True
-    except RuntimeError as e:
+    except Exception as e:
         print(f"❌ VLLM implementation failed with {num_experts} experts: {e}")
         vllm_works = False
 
@@ -257,13 +261,47 @@ def get_topk_ids(num_tokens: int, num_experts: int, topk: int) -> torch.Tensor:
     return topk_ids
 
 
+def sgl_moe_align_block_size_with_empty(
+    topk_ids,
+    num_experts,
+    block_size,
+    sorted_ids,
+    expert_ids,
+    num_tokens_post_pad,
+    pad_sorted_token_ids=False,
+):
+    if not pad_sorted_token_ids:
+        sorted_ids.fill_(topk_ids.numel())
+
+    token_cnts_buffer = torch.empty(
+        (num_experts + 1) * num_experts,
+        dtype=torch.int32,
+        device=topk_ids.device,
+    )
+    cumsum_buffer = torch.empty(
+        num_experts + 1, dtype=torch.int32, device=topk_ids.device
+    )
+
+    sgl_moe_align_block_size(
+        topk_ids,
+        num_experts,
+        block_size,
+        sorted_ids.clone(),
+        expert_ids.clone(),
+        num_tokens_post_pad.clone(),
+        token_cnts_buffer,
+        cumsum_buffer,
+        pad_sorted_token_ids,
+    )
+
+
 @triton.testing.perf_report(
     triton.testing.Benchmark(
         x_names=["num_tokens", "num_experts", "topk"],
         x_vals=configs,
         line_arg="provider",
-        line_vals=["sgl", "triton", "vllm"],
-        line_names=["SGL", "Triton", "VLLM"],
+        line_vals=["sgl", "sgl_fusion", "triton"],
+        line_names=["SGL", "SGL Fusion", "Triton"],
         styles=[("blue", "-"), ("red", "-"), ("green", "-")],
         ylabel="us",
         plot_name="moe-align-block-size-performance",
@@ -288,7 +326,6 @@ def benchmark(num_tokens, num_experts, topk, provider):
     sorted_ids = torch.empty(
         (max_num_tokens_padded,), dtype=torch.int32, device=topk_ids.device
     )
-    sorted_ids.fill_(topk_ids.numel())
     max_num_m_blocks = max_num_tokens_padded // block_size
     expert_ids = torch.empty(
         (max_num_m_blocks,), dtype=torch.int32, device=topk_ids.device
@@ -297,35 +334,18 @@ def benchmark(num_tokens, num_experts, topk, provider):
 
     quantiles = [0.5, 0.2, 0.8]
     if provider == "sgl":
-
-        def sgl_moe_align_block_size_with_empty(
-            topk_ids,
-            num_experts,
-            block_size,
-            sorted_ids,
-            expert_ids,
-            num_tokens_post_pad,
-        ):
-            token_cnts_buffer = torch.empty(
-                (num_experts + 1) * num_experts,
-                dtype=torch.int32,
-                device=topk_ids.device,
-            )
-            cumsum_buffer = torch.empty(
-                num_experts + 1, dtype=torch.int32, device=topk_ids.device
-            )
-
-            sgl_moe_align_block_size(
+        ms, min_ms, max_ms = triton.testing.do_bench(
+            lambda: sgl_moe_align_block_size_with_empty(
                 topk_ids,
                 num_experts,
                 block_size,
-                sorted_ids.clone(),
-                expert_ids.clone(),
-                num_tokens_post_pad.clone(),
-                token_cnts_buffer,
-                cumsum_buffer,
-            )
-
+                sorted_ids,
+                expert_ids,
+                num_tokens_post_pad,
+            ),
+            quantiles=quantiles,
+        )
+    elif provider == "sgl_fusion":
         ms, min_ms, max_ms = triton.testing.do_bench(
             lambda: sgl_moe_align_block_size_with_empty(
                 topk_ids,
@@ -334,10 +354,12 @@ def benchmark(num_tokens, num_experts, topk, provider):
                 sorted_ids,
                 expert_ids,
                 num_tokens_post_pad,
+                pad_sorted_token_ids=True,
             ),
             quantiles=quantiles,
         )
     elif provider == "triton":
+        sorted_ids.fill_(topk_ids.numel())
         ms, min_ms, max_ms = triton.testing.do_bench(
             lambda: moe_align_block_size_triton(
                 topk_ids,
@@ -349,23 +371,6 @@ def benchmark(num_tokens, num_experts, topk, provider):
             ),
             quantiles=quantiles,
         )
-    else:  # vllm
-        try:
-            ms, min_ms, max_ms = triton.testing.do_bench(
-                lambda: ops.moe_align_block_size(
-                    topk_ids,
-                    num_experts,
-                    block_size,
-                    sorted_ids.clone(),
-                    expert_ids.clone(),
-                    num_tokens_post_pad.clone(),
-                ),
-                quantiles=quantiles,
-            )
-        except RuntimeError as e:
-            print(f"❌ VLLM benchmark failed with {num_experts} experts: {e}")
-            # Return extreme values to indicate failure in the chart
-            return float("inf"), float("inf"), float("inf")
 
     return 1000 * ms, 1000 * max_ms, 1000 * min_ms
 

sgl-kernel/csrc/common_extension.cc

@@ -160,7 +160,8 @@ TORCH_LIBRARY_FRAGMENT(sgl_kernel, m) {
    */
   m.def(
       "moe_align_block_size(Tensor topk_ids, int num_experts, int block_size, Tensor! sorted_token_ids, Tensor! "
-      "experts_ids, Tensor! num_tokens_post_pad, Tensor! token_cnts_buffer, Tensor! cumsum_buffer) -> ()");
+      "experts_ids, Tensor! num_tokens_post_pad, Tensor! token_cnts_buffer, Tensor! cumsum_buffer, bool "
+      "pad_sorted_token_ids) -> ()");
   m.impl("moe_align_block_size", torch::kCUDA, &moe_align_block_size);
 
   m.def(

sgl-kernel/csrc/moe/moe_align_kernel.cu

@@ -21,8 +21,17 @@ limitations under the License.
 
 #include "utils.h"
 
+template <typename T, int N, int Alignment = sizeof(T) * N>
+class alignas(Alignment) AlignedArray {
+ public:
+  T data[N];
+};
+
 #define WARP_SIZE 32
 
+#define VEC_SIZE 4
+using Vec = AlignedArray<int32_t, VEC_SIZE>;
+
 template <typename scalar_t>
 __global__ void count_and_sort_expert_tokens_kernel(
     const scalar_t* __restrict__ topk_ids,
@@ -50,7 +59,8 @@ __global__ void moe_align_block_size_kernel(
     int32_t experts_per_warp,
     int32_t block_size,
     size_t numel,
-    int32_t* __restrict__ cumsum) {
+    int32_t* __restrict__ cumsum,
+    bool pad_sorted_token_ids) {
   extern __shared__ int32_t shared_counts[];
 
   const int warp_id = threadIdx.x / WARP_SIZE;
@@ -96,6 +106,24 @@ __global__ void moe_align_block_size_kernel(
       expert_ids[i / block_size] = threadIdx.x;
     }
   }
+
+  if (pad_sorted_token_ids) {
+    int32_t fill_val = static_cast<int32_t>(numel);
+    int32_t total = *total_tokens_post_pad;
+
+    Vec fill_vec;
+#pragma unroll
+    for (int i = 0; i < VEC_SIZE; ++i) {
+      fill_vec.data[i] = fill_val;
+    }
+
+    int32_t total_vec_count = (total + VEC_SIZE - 1) / VEC_SIZE;
+    Vec* out_ptr = reinterpret_cast<Vec*>(sorted_token_ids);
+
+    for (int32_t idx = tid; idx < total_vec_count; idx += stride) {
+      out_ptr[idx] = fill_vec;
+    }
+  }
 }
 
 template <typename scalar_t>
@@ -106,7 +134,8 @@ __global__ void moe_align_block_size_small_batch_expert_kernel(
     int32_t* __restrict__ total_tokens_post_pad,
     int32_t num_experts,
     int32_t block_size,
-    size_t numel) {
+    size_t numel,
+    bool pad_sorted_token_ids) {
   const size_t tid = threadIdx.x;
   const size_t stride = blockDim.x;
 
@@ -149,6 +178,26 @@ __global__ void moe_align_block_size_small_batch_expert_kernel(
     }
   }
 
+  if (pad_sorted_token_ids) {
+    int32_t fill_val = static_cast<int32_t>(numel);
+    int32_t total = *total_tokens_post_pad;
+
+    Vec fill_vec;
+#pragma unroll
+    for (int i = 0; i < VEC_SIZE; ++i) {
+      fill_vec.data[i] = fill_val;
+    }
+
+    int32_t total_vec_count = (total + VEC_SIZE - 1) / VEC_SIZE;
+    Vec* out_ptr = reinterpret_cast<Vec*>(sorted_token_ids);
+
+    for (int32_t idx = tid; idx < total_vec_count; idx += stride) {
+      out_ptr[idx] = fill_vec;
+    }
+  }
+
+  __syncthreads();
+
   for (size_t i = tid; i < numel; i += stride) {
     int32_t expert_id = topk_ids[i];
     int32_t rank_post_pad = tokens_cnts[threadIdx.x * num_experts + expert_id] + cumsum[expert_id];
@@ -165,7 +214,8 @@ void moe_align_block_size(
     torch::Tensor experts_ids,
     torch::Tensor num_tokens_post_pad,
     torch::Tensor token_cnts_buffer,
-    torch::Tensor cumsum_buffer) {
+    torch::Tensor cumsum_buffer,
+    bool pad_sorted_token_ids) {
   const cudaStream_t stream = at::cuda::getCurrentCUDAStream();
 
   int64_t padded_num_experts = ((num_experts + WARP_SIZE - 1) / WARP_SIZE) * WARP_SIZE;
@@ -190,7 +240,8 @@ void moe_align_block_size(
           num_tokens_post_pad.data_ptr<int32_t>(),
           num_experts,
           block_size,
-          topk_ids.numel());
+          topk_ids.numel(),
+          pad_sorted_token_ids);
     } else {
       auto align_kernel = moe_align_block_size_kernel<scalar_t>;
 
@@ -207,7 +258,8 @@ void moe_align_block_size(
           experts_per_warp,
           block_size,
           topk_ids.numel(),
-          cumsum_buffer.data_ptr<int32_t>());
+          cumsum_buffer.data_ptr<int32_t>(),
+          pad_sorted_token_ids);
 
       const int block_threads = std::min(256, (int)threads);
       const int num_blocks = (topk_ids.numel() + block_threads - 1) / block_threads;

sgl-kernel/csrc/torch_extension_rocm.cc

@@ -59,7 +59,8 @@ TORCH_LIBRARY_EXPAND(sgl_kernel, m) {
    */
   m.def(
       "moe_align_block_size(Tensor topk_ids, int num_experts, int block_size, Tensor! sorted_token_ids, Tensor! "
-      "experts_ids, Tensor! num_tokens_post_pad, Tensor! token_cnts_buffer, Tensor! cumsum_buffer) -> ()");
+      "experts_ids, Tensor! num_tokens_post_pad, Tensor! token_cnts_buffer, Tensor! cumsum_buffer, bool "
+      "pad_sorted_token_ids) -> ()");
   m.impl("moe_align_block_size", torch::kCUDA, &moe_align_block_size);
 
   m.def(

sgl-kernel/include/sgl_kernel_ops.h

@@ -212,7 +212,8 @@ void moe_align_block_size(
     torch::Tensor experts_ids,
     torch::Tensor num_tokens_post_pad,
     torch::Tensor token_cnts_buffer,
-    torch::Tensor cumsum_buffer);
+    torch::Tensor cumsum_buffer,
+    bool pad_sorted_token_ids);
 
 void topk_softmax(
     torch::Tensor& topk_weights,

sgl-kernel/python/sgl_kernel/moe.py

@@ -12,6 +12,7 @@ def moe_align_block_size(
     num_tokens_post_pad,
     token_cnts_buffer,
     cumsum_buffer,
+    pad_sorted_token_ids=False,
 ):
     torch.ops.sgl_kernel.moe_align_block_size.default(
         topk_ids,
@@ -22,6 +23,7 @@ def moe_align_block_size(
         num_tokens_post_pad,
         token_cnts_buffer,
         cumsum_buffer,
+        pad_sorted_token_ids,
     )
 
 

sgl-kernel/tests/test_moe_align.py

@@ -138,33 +138,32 @@ def moe_align_block_size_triton(
 
 
 @pytest.mark.parametrize(
-    "block_size,num_tokens,topk,num_experts",
+    "block_size,num_tokens,topk,num_experts,pad_sorted_token_ids",
     list(
         itertools.product(
             [32, 64, 128, 256],  # block_size
             [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096],  # num_tokens
             [1, 2, 4, 8, 16, 32, 64],  # topk
             [64, 160, 256, 257, 260, 264],  #  num_experts
+            [True, False],  # pad_sorted_token_ids
         )
     ),
 )
 def test_moe_align_block_size_compare_implementations(
-    block_size, num_tokens, topk, num_experts
+    block_size, num_tokens, topk, num_experts, pad_sorted_token_ids
 ):
 
-    topk_ids = torch.stack(
-        [
-            torch.randperm(num_experts, dtype=torch.int32, device="cuda")[:topk]
-            for _ in range(num_tokens)
-        ]
-    )
+    topk_ids = torch.argsort(torch.rand(num_tokens, num_experts, device="cuda"), dim=1)[
+        :, :topk
+    ]
 
     max_num_tokens_padded = topk_ids.numel() + num_experts * (block_size - 1)
 
     sorted_ids_cuda = torch.empty(
         (max_num_tokens_padded,), dtype=torch.int32, device=topk_ids.device
     )
-    sorted_ids_cuda.fill_(topk_ids.numel())
+    if not pad_sorted_token_ids:
+        sorted_ids_cuda.fill_(topk_ids.numel())
     max_num_m_blocks = max_num_tokens_padded // block_size
     expert_ids_cuda = torch.zeros(
         (max_num_m_blocks,), dtype=torch.int32, device=topk_ids.device
@@ -195,6 +194,7 @@ def test_moe_align_block_size_compare_implementations(
         num_tokens_post_pad_cuda,
         token_cnts_buffer,
         cumsum_buffer,
+        pad_sorted_token_ids,
     )
 
     moe_align_block_size_triton(
@@ -206,20 +206,51 @@ def test_moe_align_block_size_compare_implementations(
         num_tokens_post_pad_triton,
     )
 
-    assert torch.allclose(expert_ids_cuda, expert_ids_triton), (
+    assert torch.allclose(expert_ids_cuda, expert_ids_triton, atol=0, rtol=0), (
         f"Expert IDs mismatch for block_size={block_size}, "
         f"num_tokens={num_tokens}, topk={topk}\n"
         f"CUDA expert_ids: {expert_ids_cuda}\n"
         f"Triton expert_ids: {expert_ids_triton}"
     )
 
-    assert torch.allclose(num_tokens_post_pad_cuda, num_tokens_post_pad_triton), (
+    assert torch.allclose(
+        num_tokens_post_pad_cuda, num_tokens_post_pad_triton, atol=0, rtol=0
+    ), (
         f"Num tokens post pad mismatch for block_size={block_size}, "
         f"num_tokens={num_tokens}, topk={topk}\n"
         f"CUDA num_tokens_post_pad: {num_tokens_post_pad_cuda}\n"
         f"Triton num_tokens_post_pad: {num_tokens_post_pad_triton}"
     )
 
+    # Select an expert to check
+    expert_idx = expert_ids_cuda.max().item()
+
+    # Get the first and last block id where expert_ids_cuda == expert_idx
+    matching_indices = torch.where(expert_ids_cuda == expert_idx)[0]
+    block_sorted_start = matching_indices[0].item() * block_size
+    block_sorted_end = min(
+        (matching_indices[-1].item() + 1) * block_size, max_num_tokens_padded
+    )
+
+    selected_sorted_ids_cuda = sorted_ids_cuda[
+        block_sorted_start:block_sorted_end
+    ].sort()[0]
+    selected_sorted_ids_triton = sorted_ids_triton[
+        block_sorted_start:block_sorted_end
+    ].sort()[0]
+
+    assert torch.allclose(
+        selected_sorted_ids_cuda,
+        selected_sorted_ids_triton,
+        atol=0,
+        rtol=0,
+    ), (
+        f"Sorted IDs mismatch for block_size={block_size}, "
+        f"num_tokens={num_tokens}, topk={topk}\n"
+        f"CUDA sorted_ids: {selected_sorted_ids_cuda}\n"
+        f"Triton sorted_ids: {selected_sorted_ids_triton}"
+    )
+
 
 if __name__ == "__main__":
     pytest.main([__file__])