[Perf] Only clone when needed for `moe_permute` (#32273)

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

csrc/moe/moe_permute_unpermute_op.cu

@@ -42,7 +42,7 @@ void moe_permute(
   auto sort_workspace = torch::empty(
       {sorter_size},
       torch::dtype(torch::kInt8).device(torch::kCUDA).requires_grad(false));
-  auto copy_topk_ids = topk_ids.clone();  // copy topk_ids for preprocess
+  torch::Tensor topk_ids_for_sort = topk_ids;
   auto permuted_experts_id = torch::empty_like(topk_ids);
   auto sorted_row_idx = torch::empty_like(inv_permuted_idx);
 
@@ -62,12 +62,13 @@ void moe_permute(
     const int* expert_map_ptr = get_ptr<int>(expert_map.value());
     valid_num_ptr =
         get_ptr<int64_t>(expert_first_token_offset) + n_local_expert;
-    preprocessTopkIdLauncher(get_ptr<int>(copy_topk_ids), n_token * topk,
+    topk_ids_for_sort = topk_ids.clone();
+    preprocessTopkIdLauncher(get_ptr<int>(topk_ids_for_sort), n_token * topk,
                              expert_map_ptr, n_expert, stream);
   }
   // expert sort topk expert id and scan expert id get expert_first_token_offset
   sortAndScanExpert(
-      get_ptr<int>(copy_topk_ids), get_ptr<int>(token_expert_indices),
+      get_ptr<const int>(topk_ids_for_sort), get_ptr<int>(token_expert_indices),
       get_ptr<int>(permuted_experts_id), get_ptr<int>(sorted_row_idx),
       get_ptr<int64_t>(expert_first_token_offset), n_token, n_expert,
       n_local_expert, topk, sorter, get_ptr<int>(sort_workspace), stream);

csrc/moe/permute_unpermute_kernels/moe_permute_unpermute_kernel.cu

@@ -109,7 +109,7 @@ void computeExpertFirstTokenOffset(int const* sorted_indices,
       sorted_indices, total_indices, num_experts, expert_first_token_offset);
 }
 
-void sortAndScanExpert(int* expert_for_source_row, const int* source_rows,
+void sortAndScanExpert(const int* expert_for_source_row, const int* source_rows,
                        int* permuted_experts, int* permuted_rows,
                        int64_t* expert_first_token_offset, int num_rows,
                        int num_experts, int num_experts_per_node, int k,

csrc/moe/permute_unpermute_kernels/moe_permute_unpermute_kernel.h

@@ -48,7 +48,7 @@ void computeExpertFirstTokenOffset(int const* sorted_indices,
                                    int64_t* expert_first_token_offset,
                                    cudaStream_t stream);
 
-void sortAndScanExpert(int* expert_for_source_row, const int* source_rows,
+void sortAndScanExpert(const int* expert_for_source_row, const int* source_rows,
                        int* permuted_experts, int* permuted_rows,
                        int64_t* expert_first_token_offset, int num_rows,
                        int num_experts, int num_experts_per_node, int k,