[Perf] Optimize `group_topk` kernel, 1.9% Throughput improvement, 2.1% TPOT improvemnt (#30159)

Signed-off-by: yewentao256 <zhyanwentao@126.com>

csrc/moe/grouped_topk_kernels.cu

@@ -444,23 +444,27 @@ __device__ inline T apply_sigmoid(T val) {
   return cuda_cast<T, float>(sigmoid_accurate(f));
 }
 
-template <typename T>
+template <ScoringFunc SF, typename T>
+__device__ inline T apply_scoring(T val) {
+  if constexpr (SF == SCORING_SIGMOID) {
+    return apply_sigmoid(val);
+  } else {
+    return val;
+  }
+}
+
+template <typename T, ScoringFunc SF>
 __device__ void topk_with_k2(T* output, T const* input, T const* bias,
                              cg::thread_block_tile<32> const& tile,
                              int32_t const lane_id,
-                             int const num_experts_per_group,
-                             int const scoring_func) {
+                             int const num_experts_per_group) {
   // Get the top2 per thread
   T largest = neg_inf<T>();
   T second_largest = neg_inf<T>();
 
   if (num_experts_per_group > WARP_SIZE) {
     for (int i = lane_id; i < num_experts_per_group; i += WARP_SIZE) {
-      T value = input[i];
-      // Apply scoring function if needed
-      if (scoring_func == SCORING_SIGMOID) {
-        value = apply_sigmoid(value);
-      }
+      T value = apply_scoring<SF>(input[i]);
       value = value + bias[i];
 
       if (value > largest) {
@@ -472,11 +476,7 @@ __device__ void topk_with_k2(T* output, T const* input, T const* bias,
     }
   } else {
     for (int i = lane_id; i < num_experts_per_group; i += WARP_SIZE) {
-      T value = input[i];
-      // Apply scoring function if needed
-      if (scoring_func == SCORING_SIGMOID) {
-        value = apply_sigmoid(value);
-      }
+      T value = apply_scoring<SF>(input[i]);
       value = value + bias[i];
       largest = value;
     }
@@ -501,13 +501,12 @@ __device__ void topk_with_k2(T* output, T const* input, T const* bias,
   }
 }
 
-template <typename T>
+template <typename T, ScoringFunc SF>
 __global__ void topk_with_k2_kernel(T* output, T* input, T const* bias,
                                     int64_t const num_tokens,
                                     int64_t const num_cases,
                                     int64_t const n_group,
-                                    int64_t const num_experts_per_group,
-                                    int const scoring_func) {
+                                    int64_t const num_experts_per_group) {
   int32_t warp_id = threadIdx.x / WARP_SIZE;
   int32_t lane_id = threadIdx.x % WARP_SIZE;
 
@@ -525,21 +524,21 @@ __global__ void topk_with_k2_kernel(T* output, T* input, T const* bias,
 #if (defined(__CUDA_ARCH__) && (__CUDA_ARCH__ >= 900))
     asm volatile("griddepcontrol.wait;");
 #endif
-    topk_with_k2(output, input, group_bias, tile, lane_id,
-                 num_experts_per_group, scoring_func);
+    topk_with_k2<T, SF>(output, input, group_bias, tile, lane_id,
+                        num_experts_per_group);
   }
 #if (defined(__CUDA_ARCH__) && (__CUDA_ARCH__ >= 900))
   asm volatile("griddepcontrol.launch_dependents;");
 #endif
 }
 
-template <typename T, typename IdxT>
+template <typename T, typename IdxT, ScoringFunc SF, int NGroup = -1>
 __global__ void group_idx_and_topk_idx_kernel(
     T* scores, T const* group_scores, float* topk_values, IdxT* topk_indices,
     T const* bias, int64_t const num_tokens, int64_t const n_group,
     int64_t const topk_group, int64_t const topk, int64_t const num_experts,
     int64_t const num_experts_per_group, bool renormalize,
-    double routed_scaling_factor, int scoring_func) {
+    double routed_scaling_factor) {
   int32_t warp_id = threadIdx.x / WARP_SIZE;
   int32_t lane_id = threadIdx.x % WARP_SIZE;
   int32_t case_id =
@@ -549,6 +548,11 @@ __global__ void group_idx_and_topk_idx_kernel(
   topk_values += case_id * topk;
   topk_indices += case_id * topk;
 
+  constexpr bool kUseStaticNGroup = (NGroup > 0);
+  // use int32 to avoid implicit conversion
+  int32_t const n_group_i32 =
+      kUseStaticNGroup ? NGroup : static_cast<int32_t>(n_group);
+
   int32_t align_num_experts_per_group =
       warp_topk::round_up_to_multiple_of<WARP_SIZE>(num_experts_per_group);
 
@@ -574,13 +578,14 @@ __global__ void group_idx_and_topk_idx_kernel(
 
   if (case_id < num_tokens) {
     // calculate group_idx
-    int32_t target_num_min = WARP_SIZE - n_group + topk_group;
+    int32_t target_num_min =
+        WARP_SIZE - n_group_i32 + static_cast<int32_t>(topk_group);
     // The check is necessary to avoid abnormal input
-    if (lane_id < n_group && is_finite(group_scores[lane_id])) {
+    if (lane_id < n_group_i32 && is_finite(group_scores[lane_id])) {
       value = group_scores[lane_id];
     }
 
-    int count_equal_to_top_value = WARP_SIZE - n_group;
+    int count_equal_to_top_value = WARP_SIZE - n_group_i32;
     int pre_count_equal_to_top_value = 0;
     // Use loop to find the largset top_group
     while (count_equal_to_top_value < target_num_min) {
@@ -604,7 +609,7 @@ __global__ void group_idx_and_topk_idx_kernel(
   int count_equalto_topkth_group = 0;
   bool if_proceed_next_topk = topk_group_value != neg_inf<T>();
   if (case_id < num_tokens && if_proceed_next_topk) {
-    for (int i_group = 0; i_group < n_group; i_group++) {
+    auto process_group = [&](int i_group) {
       if ((group_scores[i_group] > topk_group_value) ||
           ((group_scores[i_group] == topk_group_value) &&
            (count_equalto_topkth_group < num_equalto_topkth_group))) {
@@ -613,11 +618,10 @@ __global__ void group_idx_and_topk_idx_kernel(
              i += WARP_SIZE) {
           T candidates = neg_inf<T>();
           if (i < num_experts_per_group) {
-            // Apply scoring function (if any) and add bias
+            // apply scoring function (if any) and add bias
             T input = scores[offset + i];
             if (is_finite(input)) {
-              T score = (scoring_func == SCORING_SIGMOID) ? apply_sigmoid(input)
-                                                          : input;
+              T score = apply_scoring<SF>(input);
               candidates = score + bias[offset + i];
             }
           }
@@ -627,6 +631,17 @@ __global__ void group_idx_and_topk_idx_kernel(
           count_equalto_topkth_group++;
         }
       }
+    };
+
+    if constexpr (kUseStaticNGroup) {
+#pragma unroll
+      for (int i_group = 0; i_group < NGroup; ++i_group) {
+        process_group(i_group);
+      }
+    } else {
+      for (int i_group = 0; i_group < n_group_i32; ++i_group) {
+        process_group(i_group);
+      }
     }
     queue.done();
     __syncwarp();
@@ -646,12 +661,13 @@ __global__ void group_idx_and_topk_idx_kernel(
       if (i < topk) {
         // Load the score value (without bias) for normalization
         T input = scores[s_topk_idx[i]];
-        value =
-            (scoring_func == SCORING_SIGMOID) ? apply_sigmoid(input) : input;
+        value = apply_scoring<SF>(input);
         s_topk_value[i] = value;
       }
-      topk_sum +=
-          cg::reduce(tile, cuda_cast<float, T>(value), cg::plus<float>());
+      if (renormalize) {
+        topk_sum +=
+            cg::reduce(tile, cuda_cast<float, T>(value), cg::plus<float>());
+      }
     }
   }
 
@@ -660,13 +676,9 @@ __global__ void group_idx_and_topk_idx_kernel(
   if (case_id < num_tokens) {
     if (if_proceed_next_topk) {
       for (int i = lane_id; i < topk; i += WARP_SIZE) {
-        float value;
-        if (renormalize) {
-          value = cuda_cast<float, T>(s_topk_value[i]) / topk_sum *
-                  routed_scaling_factor;
-        } else {
-          value = cuda_cast<float, T>(s_topk_value[i]) * routed_scaling_factor;
-        }
+        float base = cuda_cast<float, T>(s_topk_value[i]);
+        float value = renormalize ? (base / topk_sum * routed_scaling_factor)
+                                  : (base * routed_scaling_factor);
         topk_indices[i] = s_topk_idx[i];
         topk_values[i] = value;
       }
@@ -684,6 +696,45 @@ __global__ void group_idx_and_topk_idx_kernel(
 #endif
 }
 
+template <typename T, typename IdxT, ScoringFunc SF>
+inline void launch_group_idx_and_topk_kernel(
+    cudaLaunchConfig_t const& config, T* scores, T* group_scores,
+    float* topk_values, IdxT* topk_indices, T const* bias,
+    int64_t const num_tokens, int64_t const n_group, int64_t const topk_group,
+    int64_t const topk, int64_t const num_experts,
+    int64_t const num_experts_per_group, bool const renormalize,
+    double const routed_scaling_factor) {
+  auto launch = [&](auto* kernel_instance2) {
+    cudaLaunchKernelEx(&config, kernel_instance2, scores, group_scores,
+                       topk_values, topk_indices, bias, num_tokens, n_group,
+                       topk_group, topk, num_experts, num_experts_per_group,
+                       renormalize, routed_scaling_factor);
+  };
+
+  switch (n_group) {
+    case 4: {
+      launch(&group_idx_and_topk_idx_kernel<T, IdxT, SF, 4>);
+      break;
+    }
+    case 8: {
+      launch(&group_idx_and_topk_idx_kernel<T, IdxT, SF, 8>);
+      break;
+    }
+    case 16: {
+      launch(&group_idx_and_topk_idx_kernel<T, IdxT, SF, 16>);
+      break;
+    }
+    case 32: {
+      launch(&group_idx_and_topk_idx_kernel<T, IdxT, SF, 32>);
+      break;
+    }
+    default: {
+      launch(&group_idx_and_topk_idx_kernel<T, IdxT, SF>);
+      break;
+    }
+  }
+}
+
 template <typename T, typename IdxT>
 void invokeNoAuxTc(T* scores, T* group_scores, float* topk_values,
                    IdxT* topk_indices, T const* bias, int64_t const num_tokens,
@@ -694,7 +745,6 @@ void invokeNoAuxTc(T* scores, T* group_scores, float* topk_values,
                    cudaStream_t const stream = 0) {
   int64_t num_cases = num_tokens * n_group;
   int64_t topk_with_k2_num_blocks = (num_cases - 1) / NUM_WARPS_PER_BLOCK + 1;
-  auto* kernel_instance1 = &topk_with_k2_kernel<T>;
   cudaLaunchConfig_t config;
   config.gridDim = topk_with_k2_num_blocks;
   config.blockDim = BLOCK_SIZE;
@@ -705,16 +755,33 @@ void invokeNoAuxTc(T* scores, T* group_scores, float* topk_values,
   attrs[0].val.programmaticStreamSerializationAllowed = enable_pdl;
   config.numAttrs = 1;
   config.attrs = attrs;
-  cudaLaunchKernelEx(&config, kernel_instance1, group_scores, scores, bias,
-                     num_tokens, num_cases, n_group, num_experts / n_group,
-                     scoring_func);
+  auto const sf = static_cast<ScoringFunc>(scoring_func);
+  int64_t const num_experts_per_group = num_experts / n_group;
+  auto launch_topk_with_k2 = [&](auto* kernel_instance1) {
+    cudaLaunchKernelEx(&config, kernel_instance1, group_scores, scores, bias,
+                       num_tokens, num_cases, n_group, num_experts_per_group);
+  };
+  switch (sf) {
+    case SCORING_NONE: {
+      auto* kernel_instance1 = &topk_with_k2_kernel<T, SCORING_NONE>;
+      launch_topk_with_k2(kernel_instance1);
+      break;
+    }
+    case SCORING_SIGMOID: {
+      auto* kernel_instance1 = &topk_with_k2_kernel<T, SCORING_SIGMOID>;
+      launch_topk_with_k2(kernel_instance1);
+      break;
+    }
+    default:
+      // should be guarded by higher level checks.
+      TORCH_CHECK(false, "Unsupported scoring_func in invokeNoAuxTc");
+  }
 
   int64_t topk_with_k_group_num_blocks =
       (num_tokens - 1) / NUM_WARPS_PER_BLOCK + 1;
   size_t dynamic_smem_in_bytes =
       warp_topk::calc_smem_size_for_block_wide<T, int32_t>(NUM_WARPS_PER_BLOCK,
                                                            topk);
-  auto* kernel_instance2 = &group_idx_and_topk_idx_kernel<T, IdxT>;
   config.gridDim = topk_with_k_group_num_blocks;
   config.blockDim = BLOCK_SIZE;
   config.dynamicSmemBytes = dynamic_smem_in_bytes;
@@ -723,10 +790,24 @@ void invokeNoAuxTc(T* scores, T* group_scores, float* topk_values,
   attrs[0].val.programmaticStreamSerializationAllowed = enable_pdl;
   config.numAttrs = 1;
   config.attrs = attrs;
-  cudaLaunchKernelEx(&config, kernel_instance2, scores, group_scores,
-                     topk_values, topk_indices, bias, num_tokens, n_group,
-                     topk_group, topk, num_experts, num_experts / n_group,
-                     renormalize, routed_scaling_factor, scoring_func);
+  switch (sf) {
+    case SCORING_NONE: {
+      launch_group_idx_and_topk_kernel<T, IdxT, SCORING_NONE>(
+          config, scores, group_scores, topk_values, topk_indices, bias,
+          num_tokens, n_group, topk_group, topk, num_experts,
+          num_experts_per_group, renormalize, routed_scaling_factor);
+      break;
+    }
+    case SCORING_SIGMOID: {
+      launch_group_idx_and_topk_kernel<T, IdxT, SCORING_SIGMOID>(
+          config, scores, group_scores, topk_values, topk_indices, bias,
+          num_tokens, n_group, topk_group, topk, num_experts,
+          num_experts_per_group, renormalize, routed_scaling_factor);
+      break;
+    }
+    default:
+      TORCH_CHECK(false, "Unsupported scoring_func in invokeNoAuxTc");
+  }
 }
 
 #define INSTANTIATE_NOAUX_TC(T, IdxT)                                       \